├── .github └── workflows │ └── maven.yml ├── .gitignore ├── LICENSE ├── README.md ├── kata11 ├── README.md ├── pom.xml └── src │ ├── main │ └── java │ │ └── com │ │ └── github │ │ └── forax │ │ └── kata │ │ ├── Add.java │ │ ├── Expr.java │ │ ├── Mul.java │ │ ├── Value.java │ │ └── Var.java │ └── test │ └── java │ └── com │ └── github │ └── forax │ └── kata │ └── ExprTest.java ├── kata17-preview ├── README.md ├── pom.xml └── src │ ├── main │ └── java │ │ └── com │ │ └── github │ │ └── forax │ │ └── kata │ │ └── Expr.java │ └── test │ └── java │ └── com │ └── github │ └── forax │ └── kata │ └── ExprTest.java ├── kata17 ├── README.md ├── pom.xml └── src │ ├── main │ └── java │ │ └── com │ │ └── github │ │ └── forax │ │ └── kata │ │ └── Expr.java │ └── test │ └── java │ └── com │ └── github │ └── forax │ └── kata │ └── ExprTest.java ├── kata7 ├── README.md ├── pom.xml └── src │ ├── main │ └── java │ │ └── com │ │ └── github │ │ └── forax │ │ └── kata │ │ ├── Add.java │ │ ├── Expr.java │ │ ├── Expressions.java │ │ ├── Mul.java │ │ ├── Value.java │ │ └── Var.java │ └── test │ └── java │ └── com │ └── github │ └── forax │ └── kata │ ├── ExprTest.java │ └── TestHelper.java ├── kata8 ├── README.md ├── pom.xml └── src │ ├── main │ └── java │ │ └── com │ │ └── github │ │ └── forax │ │ └── kata │ │ ├── Add.java │ │ ├── Expr.java │ │ ├── Expressions.java │ │ ├── Mul.java │ │ ├── Value.java │ │ └── Var.java │ └── test │ └── java │ └── com │ └── github │ └── forax │ └── kata │ ├── ExprTest.java │ └── TestHelper.java └── pom.xml /.github/workflows/maven.yml: -------------------------------------------------------------------------------- 1 | on: 2 | push: 3 | branches: [ master ] 4 | pull_request: 5 | branches: [ master ] 6 | 7 | jobs: 8 | build: 9 | runs-on: ubuntu-latest 10 | strategy: 11 | matrix: 12 | java: [ 17 ] 13 | name: Java ${{ matrix.java }} 14 | steps: 15 | - uses: actions/checkout@v2 16 | - name: setup 17 | uses: actions/setup-java@v1 18 | with: 19 | java-version: ${{ matrix.java }} 20 | - name: build 21 | run: | 22 | mvn -B package 23 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | # Compiled class file 2 | *.class 3 | 4 | # Log file 5 | *.log 6 | 7 | # BlueJ files 8 | *.ctxt 9 | 10 | # Mobile Tools for Java (J2ME) 11 | .mtj.tmp/ 12 | 13 | # Package Files # 14 | *.jar 15 | *.war 16 | *.nar 17 | *.ear 18 | *.zip 19 | *.tar.gz 20 | *.rar 21 | 22 | # virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml 23 | hs_err_pid* 24 | 25 | # IDEA Files 26 | .idea 27 | *.iml 28 | 29 | # Maven Files 30 | target/ 31 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # kata-java17 2 | A kata to transform an existing program to use Java 17 new features 3 | 4 | ### Expression tree 5 | 6 | The idea of this kata is to implement a simple expression tree able to represent the following expressions 7 | - `Value` is a literal integer 8 | - `Add` is an integer addition 9 | - `Mul` is an integer multiplication 10 | - `Var` is a variable (it's value will be pass when evaluating the expression). 11 | 12 | Each expression is implemented by a Java class, here is an example of usage 13 | ```java 14 | Value value = new Value(13); 15 | Add add = new Add(new Value(4), new Add(new Value(3), new Value(7))); 16 | Mul mul = new Mul(new Value(4), new Add(new Value(3), new Value(7))); 17 | Var variable = new Var("a"); 18 | ``` 19 | 20 | An expression can also be constructed from a string in prefix form, operator first followed by the operands, 21 | (for example, `"+ 2 * 3 7"` is equivalent to `(2 + 3 * 7)`) using the method `parse(text)`. 22 | 23 | Once an expression is constructed, we can ask for a string representation using `toString()` or an evaluation 24 | using `eval(variableMap)`. The `variableMap` associate a name of a variable to its value. 25 | ```java 26 | Expr expr = Expr.parse("+ 4 * x 7"); 27 | System.out.println(expr); // (4 + x * 7) 28 | 29 | int result = expr.eval(Map.of("x", 3)); 30 | System.out.println(result); // 25 31 | ``` 32 | 33 | ### Kata Java versions 34 | 35 | This kata has been written using different versions of Java 36 | - Java 7 (Maven module [kata7](kata7)) 37 | - Java 8 (Maven module [kata8](kata8)) 38 | - Java 11 (Maven module [kata11](kata11)) 39 | - Java 17 (Maven module [kata17](kata17)) 40 | - Java 17 + preview feature (Maven module [kata17-preview](kata17-preview)) 41 | 42 | So you can start with a specific version and rewrite the code up to the point where you are using Java 17 43 | with the preview features enabled. 44 | -------------------------------------------------------------------------------- /kata11/README.md: -------------------------------------------------------------------------------- 1 | # kata11 2 | version of the Kata using Java 11 features 3 | 4 | ## Toward Java 17 5 | 6 | 1. [JEP 378](https://openjdk.java.net/jeps/378) introduces a syntax for multi-lines string named text block. 7 | Refactor `ExprTest.parseAll()` to use that syntax. 8 | 9 | 2. [JEP 361](https://openjdk.java.net/jeps/361) introduces two changes to the switch syntax 10 | - avoid fallthrough in switch by using `->` instead of ':' 11 | - allow a switch to be an expression (switch expression) instead of being only a statement 12 | Rewrite the code of `Expr.parse(Iterator)` to use a switch expression with the arrow syntax (`->`) 13 | 14 | 3. [JEP 394](https://openjdk.java.net/jeps/394) introduces a new form of `instanceof`. 15 | ``` 16 | Object object = ... 17 | if (object instanceof String text) { 18 | // I can use 'text' here 19 | } 20 | ``` 21 | So you can replace the `instanceof` in `Add.equals`, `Mul.equals`, `Value.equals` and `Var.equals` 22 | by a version with a type pattern. 23 | 24 | 4. [JEP 395](https://openjdk.java.net/jeps/395) introduces a new form of class named `record` 25 | that allow to declare data class, a class that defines unmodifiable data, in a simple way. 26 | So you can convert `Add`, `Mul`, `Value` and `Var` to records. 27 | 28 | 5. A record let you define a compact constructor that let you declare only the preconditions 29 | (the calls to `requireNonNull` in our case). 30 | Use compact constructors in `Add`, `Mul` and `Var`, to make the code simpler. 31 | 32 | 6. The current API has a serious issue, the interface can be implemented by anyone but at the same time, 33 | `Expr.parse()` restricts the possible implementations to `Add`, `Mul`, `Value` and `Var`. 34 | [JEP 409](https://openjdk.java.net/jeps/409) introduces the concept of sealed class that we can leverage 35 | to disallow other implementations of `Expr` than `Add`, `Mul` and `Var`. 36 | Add the keyword `sealed` and the list of permitted classes to `Expr`. 37 | 38 | 7. If all implementations of `Expr` are in the same Java file, then the compiler can infer the permitted 39 | classes automatically. Move `Add`, `Mul` and `Var` into the class `Expr` as member classes 40 | so you can omit the `permits` clause. 41 | 42 | Once all these refactoring are done, you can continue with the 43 | [migration to use Java 17 preview features](../kata17-preview/README.md). -------------------------------------------------------------------------------- /kata11/pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | kata-java17 8 | com.github.forax.kata 9 | 1.0-SNAPSHOT 10 | 11 | 12 | kata11 13 | 14 | 15 | 16 | 17 | org.apache.maven.plugins 18 | maven-compiler-plugin 19 | 3.8.1 20 | 21 | 11 22 | 11 23 | 11 24 | 25 | 26 | 27 | org.apache.maven.plugins 28 | maven-surefire-plugin 29 | 3.0.0-M5 30 | 31 | 32 | 33 | 34 | -------------------------------------------------------------------------------- /kata11/src/main/java/com/github/forax/kata/Add.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | import java.util.Objects; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public final class Add implements Expr { 9 | private final Expr left; 10 | private final Expr right; 11 | 12 | public Add(Expr left, Expr right) { 13 | requireNonNull(left); 14 | requireNonNull(right); 15 | this.left = left; 16 | this.right = right; 17 | } 18 | 19 | @Override 20 | public int eval(Map variableMap) { 21 | requireNonNull(variableMap); 22 | return left.eval(variableMap) + right.eval(variableMap); 23 | } 24 | 25 | @Override 26 | public String toString() { 27 | return "(" + left + " + " + right + ")"; 28 | } 29 | 30 | public Expr left() { 31 | return left; 32 | } 33 | 34 | public Expr right() { 35 | return right; 36 | } 37 | 38 | @Override 39 | public boolean equals(Object obj) { 40 | if (!(obj instanceof Add)) { 41 | return false; 42 | } 43 | var add = (Add) obj; 44 | return left.equals(add.left) && right.equals(add.right); 45 | } 46 | 47 | @Override 48 | public int hashCode() { 49 | return Objects.hash(left, right); 50 | } 51 | } 52 | -------------------------------------------------------------------------------- /kata11/src/main/java/com/github/forax/kata/Expr.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Iterator; 4 | import java.util.List; 5 | import java.util.Map; 6 | 7 | import static java.util.Objects.requireNonNull; 8 | 9 | public interface Expr { 10 | int eval(Map variableMap); 11 | 12 | static Expr parse(List tokens) { 13 | requireNonNull(tokens); 14 | return parse(tokens.iterator()); 15 | } 16 | 17 | private static Expr parse(Iterator iterator) { 18 | var token = iterator.next(); 19 | Expr expr; 20 | switch (token) { 21 | case "+": 22 | expr = new Add(parse(iterator), parse(iterator)); 23 | break; 24 | case "*": 25 | expr = new Mul(parse(iterator), parse(iterator)); 26 | break; 27 | default: 28 | try { 29 | expr = new Value(Integer.parseInt(token)); 30 | } catch (NumberFormatException e) { 31 | expr = new Var(token); 32 | } 33 | } 34 | return expr; 35 | } 36 | } 37 | -------------------------------------------------------------------------------- /kata11/src/main/java/com/github/forax/kata/Mul.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | import java.util.Objects; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public final class Mul implements Expr { 9 | private final Expr left; 10 | private final Expr right; 11 | 12 | public Mul(Expr left, Expr right) { 13 | requireNonNull(left); 14 | requireNonNull(right); 15 | this.left = left; 16 | this.right = right; 17 | } 18 | 19 | @Override 20 | public int eval(Map variableMap) { 21 | requireNonNull(variableMap); 22 | return left.eval(variableMap) * right.eval(variableMap); 23 | } 24 | 25 | @Override 26 | public String toString() { 27 | return left + " * " + right; 28 | } 29 | 30 | public Expr left() { 31 | return left; 32 | } 33 | 34 | public Expr right() { 35 | return right; 36 | } 37 | 38 | @Override 39 | public boolean equals(Object obj) { 40 | if (!(obj instanceof Mul)) { 41 | return false; 42 | } 43 | var mul = (Mul) obj; 44 | return left.equals(mul.left) && right.equals(mul.right); 45 | } 46 | 47 | @Override 48 | public int hashCode() { 49 | return Objects.hash(left, right); 50 | } 51 | } 52 | -------------------------------------------------------------------------------- /kata11/src/main/java/com/github/forax/kata/Value.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | 5 | import static java.util.Objects.requireNonNull; 6 | 7 | public final class Value implements Expr { 8 | private final int value; 9 | 10 | public Value(int value) { 11 | this.value = value; 12 | } 13 | 14 | @Override 15 | public int eval(Map variableMap) { 16 | requireNonNull(variableMap); 17 | return value; 18 | } 19 | 20 | @Override 21 | public String toString() { 22 | return "" + value; 23 | } 24 | 25 | public int value() { 26 | return value; 27 | } 28 | 29 | @Override 30 | public boolean equals(Object obj) { 31 | if (!(obj instanceof Value)) { 32 | return false; 33 | } 34 | var value = (Value) obj; 35 | return this.value == value.value; 36 | } 37 | 38 | @Override 39 | public int hashCode() { 40 | return value; 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /kata11/src/main/java/com/github/forax/kata/Var.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | 5 | import static java.util.Objects.requireNonNull; 6 | 7 | public final class Var implements Expr { 8 | private final String name; 9 | 10 | public Var(String name) { 11 | requireNonNull(name); 12 | this.name = name; 13 | } 14 | 15 | @Override 16 | public int eval(Map variableMap) { 17 | requireNonNull(variableMap); 18 | return variableMap.getOrDefault(name, 0); 19 | } 20 | 21 | @Override 22 | public String toString() { 23 | return name; 24 | } 25 | 26 | public String name() { 27 | return name; 28 | } 29 | 30 | @Override 31 | public boolean equals(Object obj) { 32 | if (!(obj instanceof Var)) { 33 | return false; 34 | } 35 | var variable = (Var) obj; 36 | return name.equals(variable.name); 37 | } 38 | 39 | @Override 40 | public int hashCode() { 41 | return name.hashCode(); 42 | } 43 | } 44 | -------------------------------------------------------------------------------- /kata11/src/test/java/com/github/forax/kata/ExprTest.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import org.junit.jupiter.api.Test; 4 | 5 | import java.util.List; 6 | import java.util.Map; 7 | import java.util.stream.Collectors; 8 | 9 | import static org.junit.jupiter.api.Assertions.assertAll; 10 | import static org.junit.jupiter.api.Assertions.assertEquals; 11 | import static org.junit.jupiter.api.Assertions.assertThrows; 12 | 13 | public class ExprTest { 14 | 15 | @Test 16 | public void testValue() { 17 | var value = new Value(13); 18 | assertAll( 19 | () -> assertEquals(13, value.value()), 20 | () -> assertEquals("13", value.toString()), 21 | () -> assertEquals(13, value.eval(Map.of())) 22 | ); 23 | } 24 | @Test 25 | public void testAdd() { 26 | var add = new Add(new Value(2), new Add(new Value(3), new Value(1))); 27 | assertAll( 28 | () -> assertEquals(new Value(2), add.left()), 29 | () -> assertEquals(new Add(new Value(3), new Value(1)), add.right()), 30 | () -> assertEquals("(2 + (3 + 1))", add.toString()), 31 | () -> assertEquals(6, add.eval(Map.of())), 32 | () -> assertThrows(NullPointerException.class, () -> new Add(new Value(13), null)), 33 | () -> assertThrows(NullPointerException.class, () -> new Add(null, new Value(31))) 34 | ); 35 | } 36 | @Test 37 | public void testMul() { 38 | var mul = new Mul(new Value(3), new Add(new Value(7), new Value(4))); 39 | assertAll( 40 | () -> assertEquals(new Value(3), mul.left()), 41 | () -> assertEquals(new Add(new Value(7), new Value(4)), mul.right()), 42 | () -> assertEquals("3 * (7 + 4)", mul.toString()), 43 | () -> assertEquals(33, mul.eval(Map.of())), 44 | () -> assertThrows(NullPointerException.class, () -> new Mul(new Value(13), null)), 45 | () -> assertThrows(NullPointerException.class, () -> new Mul(null, new Value(31))) 46 | ); 47 | } 48 | @Test 49 | public void testVar() { 50 | var variable = new Var("x"); 51 | assertAll( 52 | () -> assertEquals("x", variable.name()), 53 | () -> assertEquals("x", variable.toString()), 54 | () -> assertEquals(0, variable.eval(Map.of())), 55 | () -> assertEquals(42, variable.eval(Map.of("x", 42))), 56 | () -> assertThrows(NullPointerException.class, () -> new Var(null)) 57 | ); 58 | } 59 | 60 | @Test 61 | public void parse() { 62 | Expr expr = Expr.parse(List.of("+", "a", "*", "b", "3")); 63 | assertAll( 64 | () -> assertEquals(9, expr.eval(Map.of("a", 3, "b", 2))), 65 | () -> assertThrows(NullPointerException.class, () -> Expr.parse(null)) 66 | ); 67 | } 68 | 69 | @Test 70 | public void parseAll() { 71 | var exprsText = "+ a 4\n" + 72 | "+ a b\n" + 73 | "+ a * b 3\n"; 74 | 75 | var exprs = 76 | exprsText 77 | .lines() 78 | .map(line -> List.of(line.split(" "))) 79 | .map(Expr::parse) 80 | .collect(Collectors.toList()); 81 | 82 | assertEquals(List.of(7, 5, 9), 83 | exprs.stream().map(expr -> expr.eval(Map.of("a", 3, "b", 2))).collect(Collectors.toList())); 84 | } 85 | } -------------------------------------------------------------------------------- /kata17-preview/README.md: -------------------------------------------------------------------------------- 1 | # kata17-preview 2 | version of the Kata using Java 17 with the preview features enabled 3 | 4 | 5 | -------------------------------------------------------------------------------- /kata17-preview/pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | kata-java17 8 | com.github.forax.kata 9 | 1.0-SNAPSHOT 10 | 11 | 12 | kata17-preview 13 | 14 | 15 | 16 | 17 | org.apache.maven.plugins 18 | maven-compiler-plugin 19 | 3.8.1 20 | 21 | 17 22 | 17 23 | 17 24 | --enable-preview 25 | 26 | 27 | 28 | org.apache.maven.plugins 29 | maven-surefire-plugin 30 | 3.0.0-M5 31 | 32 | --enable-preview 33 | 34 | 35 | 36 | 37 | 38 | -------------------------------------------------------------------------------- /kata17-preview/src/main/java/com/github/forax/kata/Expr.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Iterator; 4 | import java.util.List; 5 | import java.util.Map; 6 | 7 | import static java.util.Objects.requireNonNull; 8 | 9 | public sealed interface Expr { 10 | default int eval(Map variableMap) { 11 | return switch (this) { 12 | case Value value -> value.value; 13 | case Add add -> add.left.eval(variableMap) + add.right.eval(variableMap); 14 | case Mul mul -> mul.left.eval(variableMap) * mul.right.eval(variableMap); 15 | case Var variable -> variableMap.getOrDefault(variable.name, 0); 16 | }; 17 | } 18 | 19 | static Expr parse(List tokens) { 20 | requireNonNull(tokens); 21 | return parse(tokens.iterator()); 22 | } 23 | 24 | private static Expr parse(Iterator iterator) { 25 | var token = iterator.next(); 26 | return switch (token) { 27 | case "+" -> new Add(parse(iterator), parse(iterator)); 28 | case "*" -> new Mul(parse(iterator), parse(iterator)); 29 | default -> { 30 | try { 31 | yield new Value(Integer.parseInt(token)); 32 | } catch(NumberFormatException e) { 33 | yield new Var(token); 34 | } 35 | } 36 | }; 37 | } 38 | 39 | record Value(int value) implements Expr { 40 | @Override 41 | public String toString() { 42 | return "" + value; 43 | } 44 | } 45 | 46 | record Add(Expr left, Expr right) implements Expr { 47 | public Add { 48 | requireNonNull(left); 49 | requireNonNull(right); 50 | } 51 | 52 | @Override 53 | public String toString() { 54 | return "(" + left + " + " + right + ")"; 55 | } 56 | } 57 | 58 | record Mul(Expr left, Expr right) implements Expr { 59 | public Mul { 60 | requireNonNull(left); 61 | requireNonNull(right); 62 | } 63 | 64 | @Override 65 | public String toString() { 66 | return left + " * " + right; 67 | } 68 | } 69 | 70 | record Var(String name) implements Expr { 71 | public Var { 72 | requireNonNull(name); 73 | } 74 | 75 | @Override 76 | public String toString() { 77 | return name; 78 | } 79 | } 80 | } 81 | -------------------------------------------------------------------------------- /kata17-preview/src/test/java/com/github/forax/kata/ExprTest.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import com.github.forax.kata.Expr.Add; 4 | import com.github.forax.kata.Expr.Mul; 5 | import com.github.forax.kata.Expr.Value; 6 | import com.github.forax.kata.Expr.Var; 7 | import org.junit.jupiter.api.Test; 8 | 9 | import java.util.List; 10 | import java.util.Map; 11 | 12 | import static org.junit.jupiter.api.Assertions.assertAll; 13 | import static org.junit.jupiter.api.Assertions.assertEquals; 14 | import static org.junit.jupiter.api.Assertions.assertThrows; 15 | 16 | public class ExprTest { 17 | 18 | @Test 19 | public void testValue() { 20 | var value = new Value(13); 21 | assertAll( 22 | () -> assertEquals(13, value.value()), 23 | () -> assertEquals("13", value.toString()), 24 | () -> assertEquals(13, value.eval(Map.of())) 25 | ); 26 | } 27 | @Test 28 | public void testAdd() { 29 | var add = new Add(new Value(2), new Add(new Value(3), new Value(1))); 30 | assertAll( 31 | () -> assertEquals(new Value(2), add.left()), 32 | () -> assertEquals(new Add(new Value(3), new Value(1)), add.right()), 33 | () -> assertEquals("(2 + (3 + 1))", add.toString()), 34 | () -> assertEquals(6, add.eval(Map.of())), 35 | () -> assertThrows(NullPointerException.class, () -> new Add(new Value(13), null)), 36 | () -> assertThrows(NullPointerException.class, () -> new Add(null, new Value(31))) 37 | ); 38 | } 39 | @Test 40 | public void testMul() { 41 | var mul = new Mul(new Value(3), new Add(new Value(7), new Value(4))); 42 | assertAll( 43 | () -> assertEquals(new Value(3), mul.left()), 44 | () -> assertEquals(new Add(new Value(7), new Value(4)), mul.right()), 45 | () -> assertEquals("3 * (7 + 4)", mul.toString()), 46 | () -> assertEquals(33, mul.eval(Map.of())), 47 | () -> assertThrows(NullPointerException.class, () -> new Mul(new Value(13), null)), 48 | () -> assertThrows(NullPointerException.class, () -> new Mul(null, new Value(31))) 49 | ); 50 | } 51 | @Test 52 | public void testVar() { 53 | var variable = new Var("x"); 54 | assertAll( 55 | () -> assertEquals("x", variable.name()), 56 | () -> assertEquals("x", variable.toString()), 57 | () -> assertEquals(0, variable.eval(Map.of())), 58 | () -> assertEquals(42, variable.eval(Map.of("x", 42))), 59 | () -> assertThrows(NullPointerException.class, () -> new Var(null)) 60 | ); 61 | } 62 | 63 | @Test 64 | public void parse() { 65 | Expr expr = Expr.parse(List.of("+", "a", "*", "b", "3")); 66 | assertAll( 67 | () -> assertEquals(9, expr.eval(Map.of("a", 3, "b", 2))), 68 | () -> assertThrows(NullPointerException.class, () -> Expr.parse(null)) 69 | ); 70 | } 71 | 72 | @Test 73 | public void parseAll() { 74 | var exprsText = """ 75 | + a 4 76 | + a b 77 | + a * b 3 78 | """; 79 | 80 | var exprs = exprsText.lines() 81 | .map(line -> List.of(line.split(" "))) 82 | .map(Expr::parse) 83 | .toList(); 84 | 85 | assertEquals(List.of(7, 5, 9), 86 | exprs.stream().map(expr -> expr.eval(Map.of("a", 3, "b", 2))).toList()); 87 | } 88 | } -------------------------------------------------------------------------------- /kata17/README.md: -------------------------------------------------------------------------------- 1 | # kata17 2 | version of the Kata using Java 17 features 3 | 4 | ## Toward Using Java 17 with the preview features enabled 5 | 6 | 1. [JEP 406](https://openjdk.java.net/jeps/406) enhances the switch to support switching on any objects. 7 | We can leverage that to simplify the code by transforming the polymorphic method `Exp.eval()` 8 | into a switch. I will make the algorithm clearer by having all bits in once place instead 9 | of having each parts declared in the implementation classes. 10 | Note: we can do that because the hierarchy is closed so we control all implementations 11 | 12 | There is a nice interaction between `sealed` and `switch()` if a hierarchy is sealed, the compiler 13 | will not allow a `default`. Which is nice because it means that if a subtype is added, the compiler 14 | will force you to add a new case. 15 | 16 | 2. That's all for now, soon [JEP 405](https://openjdk.java.net/jeps/405) 17 | will be implemented, this will avoid to use accessors in the switch, but there is no available 18 | prototype implementing that JEP yet. 19 | -------------------------------------------------------------------------------- /kata17/pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | kata-java17 8 | com.github.forax.kata 9 | 1.0-SNAPSHOT 10 | 11 | 12 | kata17 13 | 14 | 15 | 16 | 17 | org.apache.maven.plugins 18 | maven-compiler-plugin 19 | 3.8.1 20 | 21 | 17 22 | 17 23 | 17 24 | 25 | 26 | 27 | org.apache.maven.plugins 28 | maven-surefire-plugin 29 | 3.0.0-M5 30 | 31 | 32 | 33 | 34 | -------------------------------------------------------------------------------- /kata17/src/main/java/com/github/forax/kata/Expr.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Iterator; 4 | import java.util.List; 5 | import java.util.Map; 6 | 7 | import static java.util.Objects.requireNonNull; 8 | 9 | public sealed interface Expr { 10 | int eval(Map variableMap); 11 | 12 | static Expr parse(List tokens) { 13 | requireNonNull(tokens); 14 | return parse(tokens.iterator()); 15 | } 16 | 17 | private static Expr parse(Iterator iterator) { 18 | var token = iterator.next(); 19 | return switch (token) { 20 | case "+" -> new Add(parse(iterator), parse(iterator)); 21 | case "*" -> new Mul(parse(iterator), parse(iterator)); 22 | default -> { 23 | try { 24 | yield new Value(Integer.parseInt(token)); 25 | } catch(NumberFormatException e) { 26 | yield new Var(token); 27 | } 28 | } 29 | }; 30 | } 31 | 32 | record Value(int value) implements Expr { 33 | @Override 34 | public int eval(Map variableMap) { 35 | return value; 36 | } 37 | 38 | @Override 39 | public String toString() { 40 | return "" + value; 41 | } 42 | } 43 | 44 | record Add(Expr left, Expr right) implements Expr { 45 | public Add { 46 | requireNonNull(left); 47 | requireNonNull(right); 48 | } 49 | 50 | @Override 51 | public int eval(Map variableMap) { 52 | return left.eval(variableMap) + right.eval(variableMap); 53 | } 54 | 55 | @Override 56 | public String toString() { 57 | return "(" + left + " + " + right + ")"; 58 | } 59 | } 60 | 61 | record Mul(Expr left, Expr right) implements Expr { 62 | public Mul { 63 | requireNonNull(left); 64 | requireNonNull(right); 65 | } 66 | 67 | @Override 68 | public int eval(Map variableMap) { 69 | return left.eval(variableMap) * right.eval(variableMap); 70 | } 71 | 72 | @Override 73 | public String toString() { 74 | return left + " * " + right; 75 | } 76 | } 77 | 78 | record Var(String name) implements Expr { 79 | public Var { 80 | requireNonNull(name); 81 | } 82 | 83 | @Override 84 | public int eval(Map variableMap) { 85 | return variableMap.getOrDefault(name, 0); 86 | } 87 | 88 | @Override 89 | public String toString() { 90 | return name; 91 | } 92 | } 93 | } 94 | -------------------------------------------------------------------------------- /kata17/src/test/java/com/github/forax/kata/ExprTest.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import com.github.forax.kata.Expr.Add; 4 | import com.github.forax.kata.Expr.Mul; 5 | import com.github.forax.kata.Expr.Value; 6 | import com.github.forax.kata.Expr.Var; 7 | 8 | import org.junit.jupiter.api.Test; 9 | 10 | import java.util.List; 11 | import java.util.Map; 12 | 13 | import static org.junit.jupiter.api.Assertions.assertAll; 14 | import static org.junit.jupiter.api.Assertions.assertEquals; 15 | import static org.junit.jupiter.api.Assertions.assertThrows; 16 | 17 | public class ExprTest { 18 | 19 | @Test 20 | public void testValue() { 21 | var value = new Value(13); 22 | assertAll( 23 | () -> assertEquals(13, value.value()), 24 | () -> assertEquals("13", value.toString()), 25 | () -> assertEquals(13, value.eval(Map.of())) 26 | ); 27 | } 28 | @Test 29 | public void testAdd() { 30 | var add = new Add(new Value(2), new Add(new Value(3), new Value(1))); 31 | assertAll( 32 | () -> assertEquals(new Value(2), add.left()), 33 | () -> assertEquals(new Add(new Value(3), new Value(1)), add.right()), 34 | () -> assertEquals("(2 + (3 + 1))", add.toString()), 35 | () -> assertEquals(6, add.eval(Map.of())), 36 | () -> assertThrows(NullPointerException.class, () -> new Add(new Value(13), null)), 37 | () -> assertThrows(NullPointerException.class, () -> new Add(null, new Value(31))) 38 | ); 39 | } 40 | @Test 41 | public void testMul() { 42 | var mul = new Mul(new Value(3), new Add(new Value(7), new Value(4))); 43 | assertAll( 44 | () -> assertEquals(new Value(3), mul.left()), 45 | () -> assertEquals(new Add(new Value(7), new Value(4)), mul.right()), 46 | () -> assertEquals("3 * (7 + 4)", mul.toString()), 47 | () -> assertEquals(33, mul.eval(Map.of())), 48 | () -> assertThrows(NullPointerException.class, () -> new Mul(new Value(13), null)), 49 | () -> assertThrows(NullPointerException.class, () -> new Mul(null, new Value(31))) 50 | ); 51 | } 52 | @Test 53 | public void testVar() { 54 | var variable = new Var("x"); 55 | assertAll( 56 | () -> assertEquals("x", variable.name()), 57 | () -> assertEquals("x", variable.toString()), 58 | () -> assertEquals(0, variable.eval(Map.of())), 59 | () -> assertEquals(42, variable.eval(Map.of("x", 42))), 60 | () -> assertThrows(NullPointerException.class, () -> new Var(null)) 61 | ); 62 | } 63 | 64 | @Test 65 | public void parse() { 66 | Expr expr = Expr.parse(List.of("+", "a", "*", "b", "3")); 67 | assertAll( 68 | () -> assertEquals(9, expr.eval(Map.of("a", 3, "b", 2))), 69 | () -> assertThrows(NullPointerException.class, () -> Expr.parse(null)) 70 | ); 71 | } 72 | 73 | @Test 74 | public void parseAll() { 75 | var exprsText = """ 76 | + a 4 77 | + a b 78 | + a * b 3 79 | """; 80 | 81 | var exprs = exprsText.lines() 82 | .map(line -> List.of(line.split(" "))) 83 | .map(Expr::parse) 84 | .toList(); 85 | 86 | assertEquals(List.of(7, 5, 9), 87 | exprs.stream().map(expr -> expr.eval(Map.of("a", 3, "b", 2))).toList()); 88 | } 89 | } -------------------------------------------------------------------------------- /kata7/README.md: -------------------------------------------------------------------------------- 1 | # kata7 2 | version of the Kata using Java 7 features 3 | 4 | ### Test with JUnit 4 5 | JUnit 5 is compatible with Java 8+, so the [testing class](src/test/java/com/github/forax/kata/ExprTest.java) 6 | uses the previous versions of JUnit, JUnit 4. 7 | 8 | ### Toward Java 8 9 | 10 | 1. We first need to [migrate](https://junit.org/junit5/docs/current/user-guide/#migrating-from-junit4) 11 | all the tests from JUnit 4 to JUnit 5. 12 | - use @Test from `org.junit.Test` instead of `@Test` from ``org.junit.jupiter.api.Test 13 | - use `org.junit.jupiter.api.Assertions` instead of `org.junit.Assert` for methods like `assert*` 14 | - use `assertThrows(NPE.class, ...)` instead of `org.junit.Test(expected=NPE.class)` 15 | - group all `assert*` by wrapping them inside a `insertAll(...)` 16 | 17 | 2. In `ExprTest`, as part of the introduction of lambda ([JCP 335](https://www.jcp.org/en/jsr/detail?id=335)), 18 | the inference of method has been overhauled so explicitly indicating the type arguments in front of 19 | `listOf` and `mapOf` is not necessary anymore. 20 | 21 | 3. In the method `ExprTest.parseAll`, the two loops can be re-written using 22 | [streams](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/stream/package-summary.html). 23 | Note: BufferedReader has a method 24 | [lines()](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/io/BufferedReader.html#lines()) 25 | that returns a stream. 26 | 27 | 4. In `Var.eval()`, instead of using `Map.get()`, we can use 28 | [Map.getOrDefault()](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/Map.html#getOrDefault(java.lang.Object,V)) 29 | to simplify a little bit the code. 30 | 31 | Once all these refactoring are done, you can continue with the [migration to Java 11](../kata11/README.md). 32 | 33 | 34 | -------------------------------------------------------------------------------- /kata7/pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 6 | kata-java17 7 | com.github.forax.kata 8 | 1.0-SNAPSHOT 9 | 10 | 4.0.0 11 | 12 | kata7 13 | 14 | 15 | 16 | junit 17 | junit 18 | 4.13.2 19 | test 20 | 21 | 22 | org.junit.vintage 23 | junit-vintage-engine 24 | 5.8.1 25 | test 26 | 27 | 28 | 29 | 30 | 31 | 32 | org.apache.maven.plugins 33 | maven-compiler-plugin 34 | 3.8.1 35 | 36 | 7 37 | 7 38 | 7 39 | 40 | 41 | 42 | org.apache.maven.plugins 43 | maven-surefire-plugin 44 | 3.0.0-M5 45 | 46 | 47 | 48 | 49 | -------------------------------------------------------------------------------- /kata7/src/main/java/com/github/forax/kata/Add.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | import java.util.Objects; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public final class Add implements Expr { 9 | private final Expr left; 10 | private final Expr right; 11 | 12 | public Add(Expr left, Expr right) { 13 | requireNonNull(left); 14 | requireNonNull(right); 15 | this.left = left; 16 | this.right = right; 17 | } 18 | 19 | @Override 20 | public int eval(Map variableMap) { 21 | requireNonNull(variableMap); 22 | return left.eval(variableMap) + right.eval(variableMap); 23 | } 24 | 25 | @Override 26 | public String toString() { 27 | return "(" + left + " + " + right + ")"; 28 | } 29 | 30 | public Expr left() { 31 | return left; 32 | } 33 | 34 | public Expr right() { 35 | return right; 36 | } 37 | 38 | @Override 39 | public boolean equals(Object obj) { 40 | if (!(obj instanceof Add)) { 41 | return false; 42 | } 43 | Add add = (Add) obj; 44 | return left.equals(add.left) && right.equals(add.right); 45 | } 46 | 47 | @Override 48 | public int hashCode() { 49 | return Objects.hash(left, right); 50 | } 51 | } 52 | -------------------------------------------------------------------------------- /kata7/src/main/java/com/github/forax/kata/Expr.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.List; 4 | import java.util.Map; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public interface Expr { 9 | int eval(Map variableMap); 10 | } 11 | -------------------------------------------------------------------------------- /kata7/src/main/java/com/github/forax/kata/Expressions.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Iterator; 4 | import java.util.List; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public class Expressions { 9 | private Expressions() { 10 | throw new AssertionError(); 11 | } 12 | 13 | public static Expr parse(List tokens) { 14 | requireNonNull(tokens); 15 | return parse(tokens.iterator()); 16 | } 17 | 18 | private static Expr parse(Iterator iterator) { 19 | String token = iterator.next(); 20 | Expr expr; 21 | switch (token) { 22 | case "+": 23 | expr = new Add(parse(iterator), parse(iterator)); 24 | break; 25 | case "*": 26 | expr = new Mul(parse(iterator), parse(iterator)); 27 | break; 28 | default: 29 | try { 30 | expr = new Value(Integer.parseInt(token)); 31 | } catch (NumberFormatException e) { 32 | expr = new Var(token); 33 | } 34 | } 35 | return expr; 36 | } 37 | } 38 | -------------------------------------------------------------------------------- /kata7/src/main/java/com/github/forax/kata/Mul.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | import java.util.Objects; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public final class Mul implements Expr { 9 | private final Expr left; 10 | private final Expr right; 11 | 12 | public Mul(Expr left, Expr right) { 13 | requireNonNull(left); 14 | requireNonNull(right); 15 | this.left = left; 16 | this.right = right; 17 | } 18 | 19 | @Override 20 | public int eval(Map variableMap) { 21 | requireNonNull(variableMap); 22 | return left.eval(variableMap) * right.eval(variableMap); 23 | } 24 | 25 | @Override 26 | public String toString() { 27 | return left + " * " + right; 28 | } 29 | 30 | public Expr left() { 31 | return left; 32 | } 33 | 34 | public Expr right() { 35 | return right; 36 | } 37 | 38 | @Override 39 | public boolean equals(Object obj) { 40 | if (!(obj instanceof Mul)) { 41 | return false; 42 | } 43 | Mul mul = (Mul) obj; 44 | return left.equals(mul.left) && right.equals(mul.right); 45 | } 46 | 47 | @Override 48 | public int hashCode() { 49 | return Objects.hash(left, right); 50 | } 51 | } 52 | -------------------------------------------------------------------------------- /kata7/src/main/java/com/github/forax/kata/Value.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | 5 | import static java.util.Objects.requireNonNull; 6 | 7 | public final class Value implements Expr { 8 | private final int value; 9 | 10 | public Value(int value) { 11 | this.value = value; 12 | } 13 | 14 | @Override 15 | public int eval(Map variableMap) { 16 | requireNonNull(variableMap); 17 | return value; 18 | } 19 | 20 | @Override 21 | public String toString() { 22 | return "" + value; 23 | } 24 | 25 | public int value() { 26 | return value; 27 | } 28 | 29 | @Override 30 | public boolean equals(Object obj) { 31 | if (!(obj instanceof Value)) { 32 | return false; 33 | } 34 | Value value = (Value) obj; 35 | return this.value == value.value; 36 | } 37 | 38 | @Override 39 | public int hashCode() { 40 | return value; 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /kata7/src/main/java/com/github/forax/kata/Var.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | 5 | import static java.util.Objects.requireNonNull; 6 | 7 | public final class Var implements Expr { 8 | private final String name; 9 | 10 | public Var(String name) { 11 | requireNonNull(name); 12 | this.name = name; 13 | } 14 | 15 | @Override 16 | public int eval(Map variableMap) { 17 | requireNonNull(variableMap); 18 | Integer result = variableMap.get(name); 19 | return result == null? 0: result; 20 | } 21 | 22 | @Override 23 | public String toString() { 24 | return name; 25 | } 26 | 27 | public String name() { 28 | return name; 29 | } 30 | 31 | @Override 32 | public boolean equals(Object obj) { 33 | if (!(obj instanceof Var)) { 34 | return false; 35 | } 36 | Var variable = (Var) obj; 37 | return name.equals(variable.name); 38 | } 39 | 40 | @Override 41 | public int hashCode() { 42 | return name.hashCode(); 43 | } 44 | } 45 | -------------------------------------------------------------------------------- /kata7/src/test/java/com/github/forax/kata/ExprTest.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import org.junit.Test; 4 | 5 | import java.io.BufferedReader; 6 | import java.io.IOException; 7 | import java.io.StringReader; 8 | import java.util.ArrayList; 9 | import java.util.List; 10 | 11 | import static com.github.forax.kata.TestHelper.listOf; 12 | import static com.github.forax.kata.TestHelper.mapOf; 13 | 14 | import static org.junit.Assert.assertEquals; 15 | 16 | 17 | public class ExprTest { 18 | 19 | @Test 20 | public void testValue() { 21 | Value value = new Value(13); 22 | assertEquals(13, value.value()); 23 | assertEquals("13", value.toString()); 24 | assertEquals(13, value.eval(TestHelper.mapOf())); 25 | } 26 | @Test 27 | public void testAdd() { 28 | Add add = new Add(new Value(2), new Add(new Value(3), new Value(1))); 29 | assertEquals(new Value(2), add.left()); 30 | assertEquals(new Add(new Value(3), new Value(1)), add.right()); 31 | assertEquals("(2 + (3 + 1))", add.toString()); 32 | assertEquals(6, add.eval(TestHelper.mapOf())); 33 | } 34 | @Test(expected = NullPointerException.class) 35 | public void testAddPrecondition1() { 36 | new Add(new Value(13), null); 37 | } 38 | @Test(expected = NullPointerException.class) 39 | public void testAddPrecondition2() { 40 | new Add(null, new Value(31)); 41 | } 42 | 43 | @Test 44 | public void testMul() { 45 | Mul mul = new Mul(new Value(3), new Add(new Value(7), new Value(4))); 46 | assertEquals(new Value(3), mul.left()); 47 | assertEquals(new Add(new Value(7), new Value(4)), mul.right()); 48 | assertEquals("3 * (7 + 4)", mul.toString()); 49 | assertEquals(33, mul.eval(TestHelper.mapOf())); 50 | } 51 | @Test(expected = NullPointerException.class) 52 | public void testMulPrecondition1() { 53 | new Mul(new Value(13), null); 54 | } 55 | @Test(expected = NullPointerException.class) 56 | public void testMulPrecondition2() { 57 | new Mul(null, new Value(31)); 58 | } 59 | 60 | @Test 61 | public void testVar() { 62 | Var variable = new Var("x"); 63 | assertEquals("x", variable.name()); 64 | assertEquals("x", variable.toString()); 65 | assertEquals(0, variable.eval(TestHelper.mapOf())); 66 | assertEquals(42, variable.eval(mapOf("x", 42))); 67 | } 68 | @Test(expected = NullPointerException.class) 69 | public void testVarPrecondition() { 70 | new Var(null); 71 | } 72 | 73 | @Test 74 | public void parse() { 75 | Expr expr = Expressions.parse(listOf("+", "a", "*", "b", "3")); 76 | assertEquals(9, expr.eval(mapOf("a", 3, "b", 2))); 77 | } 78 | @Test(expected = NullPointerException.class) 79 | public void parsePrecondition() { 80 | Expressions.parse(null); 81 | } 82 | 83 | @Test 84 | public void parseAll() throws IOException { 85 | String exprsText = "+ a 4\n" + 86 | "+ a b\n" + 87 | "+ a * b 3\n"; 88 | 89 | ArrayList exprs = new ArrayList<>(); 90 | StringReader stringReader = new StringReader(exprsText); 91 | BufferedReader bufferedReader = new BufferedReader(stringReader); 92 | String line; 93 | while((line = bufferedReader.readLine()) != null) { 94 | List tokens = listOf(line.split(" ")); 95 | Expr expr = Expressions.parse(tokens); 96 | exprs.add(expr); 97 | } 98 | 99 | ArrayList results = new ArrayList<>(); 100 | for(Expr expr: exprs) { 101 | int result = expr.eval(mapOf("a", 3, "b", 2)); 102 | results.add(result); 103 | } 104 | 105 | assertEquals(listOf(7, 5, 9), results); 106 | } 107 | } -------------------------------------------------------------------------------- /kata7/src/test/java/com/github/forax/kata/TestHelper.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.ArrayList; 4 | import java.util.Collections; 5 | import java.util.HashMap; 6 | import java.util.List; 7 | import java.util.Map; 8 | 9 | import static java.util.Objects.requireNonNull; 10 | 11 | class TestHelper { 12 | private TestHelper() { 13 | throw new AssertionError(); 14 | } 15 | 16 | @SafeVarargs 17 | public static List listOf(T... elements) { 18 | ArrayList list = new ArrayList<>(); 19 | for(T element: elements) { 20 | list.add(requireNonNull(element)); 21 | } 22 | return Collections.unmodifiableList(list); 23 | } 24 | 25 | public static Map mapOf() { 26 | return Collections.emptyMap(); 27 | } 28 | public static Map mapOf(K key1, V value1) { 29 | requireNonNull(key1); 30 | requireNonNull(value1); 31 | return Collections.singletonMap(key1, value1); 32 | } 33 | public static Map mapOf(K key1, V value1, K key2, V value2) { 34 | requireNonNull(key1); 35 | requireNonNull(value1); 36 | requireNonNull(key2); 37 | requireNonNull(value2); 38 | if (key1.equals(key2)) { 39 | throw new IllegalArgumentException(); 40 | } 41 | HashMap map = new HashMap<>(); 42 | map.put(key1, value1); 43 | map.put(key2, value2); 44 | return Collections.unmodifiableMap(map); 45 | } 46 | } 47 | -------------------------------------------------------------------------------- /kata8/README.md: -------------------------------------------------------------------------------- 1 | # kata8 2 | version of the Kata using Java 8 features 3 | 4 | ## Toward Java 11 5 | 6 | 1. [JEP 269](https://openjdk.java.net/jeps/269) introduces convenient factory methods to create 7 | unmodifiable lists and maps. Rewrite `ExprTest` to use `List.of(...)` and `Map.of(...)` 8 | and remove the class `TestHelper` which is not needed anymore. 9 | 10 | 2. Java 11 adds a method 11 | [String.lines()](https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/lang/String.html#lines()) 12 | to the API. 13 | In `ExprTests.parseAll()`, the code can be simplified leveraging `String.lines()` 14 | instead of creating a `StringReader` and a `BufferedReader`. 15 | 16 | 3. [JEP 213](https://openjdk.java.net/jeps/213) allow private methods to be declared in interface. 17 | The class `Expressions` is not necessary anymore because the code of `Expressions.parse(Iterator)` 18 | can be moved into `Expr`. 19 | 20 | 4. [JEP 286](https://openjdk.java.net/jeps/286) introduces local variable type inference using 'var' so 21 | all local variable declarations can be rewritten using 'var'. 22 | 23 | Once all these refactoring are done, you can continue with the [migration to Java 17](../kata17/README.md). 24 | -------------------------------------------------------------------------------- /kata8/pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | kata-java17 8 | com.github.forax.kata 9 | 1.0-SNAPSHOT 10 | 11 | 12 | kata8 13 | 14 | 15 | 16 | 17 | org.apache.maven.plugins 18 | maven-compiler-plugin 19 | 3.8.1 20 | 21 | 8 22 | 8 23 | 8 24 | 25 | 26 | 27 | org.apache.maven.plugins 28 | maven-surefire-plugin 29 | 3.0.0-M5 30 | 31 | 32 | 33 | 34 | -------------------------------------------------------------------------------- /kata8/src/main/java/com/github/forax/kata/Add.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | import java.util.Objects; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public final class Add implements Expr { 9 | private final Expr left; 10 | private final Expr right; 11 | 12 | public Add(Expr left, Expr right) { 13 | requireNonNull(left); 14 | requireNonNull(right); 15 | this.left = left; 16 | this.right = right; 17 | } 18 | 19 | @Override 20 | public int eval(Map variableMap) { 21 | requireNonNull(variableMap); 22 | return left.eval(variableMap) + right.eval(variableMap); 23 | } 24 | 25 | @Override 26 | public String toString() { 27 | return "(" + left + " + " + right + ")"; 28 | } 29 | 30 | public Expr left() { 31 | return left; 32 | } 33 | 34 | public Expr right() { 35 | return right; 36 | } 37 | 38 | @Override 39 | public boolean equals(Object obj) { 40 | if (!(obj instanceof Add)) { 41 | return false; 42 | } 43 | Add add = (Add) obj; 44 | return left.equals(add.left) && right.equals(add.right); 45 | } 46 | 47 | @Override 48 | public int hashCode() { 49 | return Objects.hash(left, right); 50 | } 51 | } 52 | -------------------------------------------------------------------------------- /kata8/src/main/java/com/github/forax/kata/Expr.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.List; 4 | import java.util.Map; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public interface Expr { 9 | int eval(Map variableMap); 10 | 11 | static Expr parse(List tokens) { 12 | requireNonNull(tokens); 13 | return Expressions.parse(tokens.iterator()); 14 | } 15 | } 16 | -------------------------------------------------------------------------------- /kata8/src/main/java/com/github/forax/kata/Expressions.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Iterator; 4 | 5 | class Expressions { 6 | private Expressions() { 7 | throw new AssertionError(); 8 | } 9 | 10 | static Expr parse(Iterator iterator) { 11 | String token = iterator.next(); 12 | Expr expr; 13 | switch (token) { 14 | case "+": 15 | expr = new Add(parse(iterator), parse(iterator)); 16 | break; 17 | case "*": 18 | expr = new Mul(parse(iterator), parse(iterator)); 19 | break; 20 | default: 21 | try { 22 | expr = new Value(Integer.parseInt(token)); 23 | } catch (NumberFormatException e) { 24 | expr = new Var(token); 25 | } 26 | } 27 | return expr; 28 | } 29 | } 30 | -------------------------------------------------------------------------------- /kata8/src/main/java/com/github/forax/kata/Mul.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | import java.util.Objects; 5 | 6 | import static java.util.Objects.requireNonNull; 7 | 8 | public final class Mul implements Expr { 9 | private final Expr left; 10 | private final Expr right; 11 | 12 | public Mul(Expr left, Expr right) { 13 | requireNonNull(left); 14 | requireNonNull(right); 15 | this.left = left; 16 | this.right = right; 17 | } 18 | 19 | @Override 20 | public int eval(Map variableMap) { 21 | requireNonNull(variableMap); 22 | return left.eval(variableMap) * right.eval(variableMap); 23 | } 24 | 25 | @Override 26 | public String toString() { 27 | return left + " * " + right; 28 | } 29 | 30 | public Expr left() { 31 | return left; 32 | } 33 | 34 | public Expr right() { 35 | return right; 36 | } 37 | 38 | @Override 39 | public boolean equals(Object obj) { 40 | if (!(obj instanceof Mul)) { 41 | return false; 42 | } 43 | Mul mul = (Mul) obj; 44 | return left.equals(mul.left) && right.equals(mul.right); 45 | } 46 | 47 | @Override 48 | public int hashCode() { 49 | return Objects.hash(left, right); 50 | } 51 | } 52 | -------------------------------------------------------------------------------- /kata8/src/main/java/com/github/forax/kata/Value.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | 5 | import static java.util.Objects.requireNonNull; 6 | 7 | public final class Value implements Expr { 8 | private final int value; 9 | 10 | public Value(int value) { 11 | this.value = value; 12 | } 13 | 14 | @Override 15 | public int eval(Map variableMap) { 16 | requireNonNull(variableMap); 17 | return value; 18 | } 19 | 20 | @Override 21 | public String toString() { 22 | return "" + value; 23 | } 24 | 25 | public int value() { 26 | return value; 27 | } 28 | 29 | @Override 30 | public boolean equals(Object obj) { 31 | if (!(obj instanceof Value)) { 32 | return false; 33 | } 34 | Value value = (Value) obj; 35 | return this.value == value.value; 36 | } 37 | 38 | @Override 39 | public int hashCode() { 40 | return value; 41 | } 42 | } 43 | -------------------------------------------------------------------------------- /kata8/src/main/java/com/github/forax/kata/Var.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.Map; 4 | 5 | import static java.util.Objects.requireNonNull; 6 | 7 | public final class Var implements Expr { 8 | private final String name; 9 | 10 | public Var(String name) { 11 | requireNonNull(name); 12 | this.name = name; 13 | } 14 | 15 | @Override 16 | public int eval(Map variableMap) { 17 | requireNonNull(variableMap); 18 | return variableMap.getOrDefault(name, 0); 19 | } 20 | 21 | @Override 22 | public String toString() { 23 | return name; 24 | } 25 | 26 | public String name() { 27 | return name; 28 | } 29 | 30 | @Override 31 | public boolean equals(Object obj) { 32 | if (!(obj instanceof Var)) { 33 | return false; 34 | } 35 | Var variable = (Var) obj; 36 | return name.equals(variable.name); 37 | } 38 | 39 | @Override 40 | public int hashCode() { 41 | return name.hashCode(); 42 | } 43 | } 44 | -------------------------------------------------------------------------------- /kata8/src/test/java/com/github/forax/kata/ExprTest.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import org.junit.jupiter.api.Test; 4 | 5 | import java.io.BufferedReader; 6 | import java.io.StringReader; 7 | import java.util.List; 8 | import java.util.stream.Collectors; 9 | 10 | import static com.github.forax.kata.TestHelper.listOf; 11 | import static com.github.forax.kata.TestHelper.mapOf; 12 | 13 | import static org.junit.jupiter.api.Assertions.assertAll; 14 | import static org.junit.jupiter.api.Assertions.assertEquals; 15 | import static org.junit.jupiter.api.Assertions.assertThrows; 16 | 17 | public class ExprTest { 18 | 19 | @Test 20 | public void testValue() { 21 | Value value = new Value(13); 22 | assertAll( 23 | () -> assertEquals(13, value.value()), 24 | () -> assertEquals("13", value.toString()), 25 | () -> assertEquals(13, value.eval(mapOf())) 26 | ); 27 | } 28 | @Test 29 | public void testAdd() { 30 | Add add = new Add(new Value(2), new Add(new Value(3), new Value(1))); 31 | assertAll( 32 | () -> assertEquals(new Value(2), add.left()), 33 | () -> assertEquals(new Add(new Value(3), new Value(1)), add.right()), 34 | () -> assertEquals("(2 + (3 + 1))", add.toString()), 35 | () -> assertEquals(6, add.eval(mapOf())), 36 | () -> assertThrows(NullPointerException.class, () -> new Add(new Value(13), null)), 37 | () -> assertThrows(NullPointerException.class, () -> new Add(null, new Value(31))) 38 | ); 39 | } 40 | @Test 41 | public void testMul() { 42 | Mul mul = new Mul(new Value(3), new Add(new Value(7), new Value(4))); 43 | assertAll( 44 | () -> assertEquals(new Value(3), mul.left()), 45 | () -> assertEquals(new Add(new Value(7), new Value(4)), mul.right()), 46 | () -> assertEquals("3 * (7 + 4)", mul.toString()), 47 | () -> assertEquals(33, mul.eval(mapOf())), 48 | () -> assertThrows(NullPointerException.class, () -> new Mul(new Value(13), null)), 49 | () -> assertThrows(NullPointerException.class, () -> new Mul(null, new Value(31))) 50 | ); 51 | } 52 | @Test 53 | public void testVar() { 54 | Var variable = new Var("x"); 55 | assertAll( 56 | () -> assertEquals("x", variable.name()), 57 | () -> assertEquals("x", variable.toString()), 58 | () -> assertEquals(0, variable.eval(mapOf())), 59 | () -> assertEquals(42, variable.eval(mapOf("x", 42))), 60 | () -> assertThrows(NullPointerException.class, () -> new Var(null)) 61 | ); 62 | } 63 | 64 | @Test 65 | public void parse() { 66 | Expr expr = Expr.parse(listOf("+", "a", "*", "b", "3")); 67 | assertAll( 68 | () -> assertEquals(9, expr.eval(mapOf("a", 3, "b", 2))), 69 | () -> assertThrows(NullPointerException.class, () -> Expr.parse(null)) 70 | ); 71 | } 72 | 73 | @Test 74 | public void parseAll() { 75 | String exprsText = "+ a 4\n" + 76 | "+ a b\n" + 77 | "+ a * b 3\n"; 78 | 79 | List exprs = 80 | new BufferedReader(new StringReader(exprsText)) 81 | .lines() 82 | .map(line -> listOf(line.split(" "))) 83 | .map(Expr::parse) 84 | .collect(Collectors.toList()); 85 | 86 | assertEquals(listOf(7, 5, 9), 87 | exprs.stream().map(expr -> expr.eval(mapOf("a", 3, "b", 2))).collect(Collectors.toList())); 88 | } 89 | } -------------------------------------------------------------------------------- /kata8/src/test/java/com/github/forax/kata/TestHelper.java: -------------------------------------------------------------------------------- 1 | package com.github.forax.kata; 2 | 3 | import java.util.ArrayList; 4 | import java.util.Collections; 5 | import java.util.HashMap; 6 | import java.util.List; 7 | import java.util.Map; 8 | 9 | import static java.util.Objects.requireNonNull; 10 | 11 | class TestHelper { 12 | private TestHelper() { 13 | throw new AssertionError(); 14 | } 15 | 16 | @SafeVarargs 17 | public static List listOf(T... elements) { 18 | ArrayList list = new ArrayList<>(); 19 | for(T element: elements) { 20 | list.add(requireNonNull(element)); 21 | } 22 | return Collections.unmodifiableList(list); 23 | } 24 | 25 | public static Map mapOf() { 26 | return Collections.emptyMap(); 27 | } 28 | public static Map mapOf(K key1, V value1) { 29 | requireNonNull(key1); 30 | requireNonNull(value1); 31 | return Collections.singletonMap(key1, value1); 32 | } 33 | public static Map mapOf(K key1, V value1, K key2, V value2) { 34 | requireNonNull(key1); 35 | requireNonNull(value1); 36 | requireNonNull(key2); 37 | requireNonNull(value2); 38 | if (key1.equals(key2)) { 39 | throw new IllegalArgumentException(); 40 | } 41 | HashMap map = new HashMap<>(); 42 | map.put(key1, value1); 43 | map.put(key2, value2); 44 | return Collections.unmodifiableMap(map); 45 | } 46 | } 47 | -------------------------------------------------------------------------------- /pom.xml: -------------------------------------------------------------------------------- 1 | 2 | 5 | 4.0.0 6 | 7 | com.github.forax.kata 8 | kata-java17 9 | pom 10 | 1.0-SNAPSHOT 11 | 12 | kata7 13 | kata8 14 | kata11 15 | kata17 16 | kata17-preview 17 | 18 | 19 | 20 | UTF-8 21 | 22 | 23 | 24 | 25 | org.junit.jupiter 26 | junit-jupiter-api 27 | 5.8.1 28 | test 29 | 30 | 31 | org.junit.jupiter 32 | junit-jupiter-engine 33 | 5.8.1 34 | test 35 | 36 | 37 | --------------------------------------------------------------------------------