Kotlin vs Java
final var file = new File("file.txt");
3 | val file = File("file.txt")
4 | public final class User {
5 | }
6 | class User
7 | public class User {
8 | }
9 | open class User
10 | final class User {
11 | private final String name;
12 |
13 | public User(String name) {
14 | this.name = name;
15 | }
16 |
17 | public String getName() {
18 | return name;
19 | }
20 | }
21 | class User(val name: String)
22 | final class User {
23 | private String name;
24 |
25 | public User(String name) {
26 | this.name = name;
27 | }
28 |
29 | public String getName() {
30 | return name;
31 | }
32 |
33 | public void setName(String name) {
34 | this.name = name;
35 | }
36 | }
37 | class User(var name: String)
38 | final class User {
39 | private String name;
40 | private String lastName;
41 |
42 | public User(String name) {
43 | this(name, "");
44 | }
45 |
46 | public User(String name, String lastName) {
47 | this.name = name;
48 | this.lastName = lastName;
49 | }
50 |
51 | // And Getters & Setters
52 | }
53 | class User(var name: String, var lastName: String = "")
54 | public class Document {
55 |
56 | private String id = "00x";
57 |
58 | public String getId() {
59 | return id;
60 | }
61 |
62 | public void setId(String id) {
63 | if (id != null && !id.isEmpty()) {
64 | this.id = id;
65 | }
66 | }
67 |
68 | }
69 | class Document{
70 | var id : String = "00x"
71 | set(value) {
72 | if(value.isNotEmpty()) field = value
73 | }
74 | }
75 | public abstract class Document{
76 | public abstract int calculateSize();
77 | }
78 |
79 | public class Photo extends Document{
80 | @Override
81 | public int calculateSize() {
82 |
83 | }
84 | }
85 | abstract class Document {
86 | abstract fun calculateSize(): Int
87 | }
88 |
89 | class Photo : Document() {
90 | override fun calculateSize(): Int {
91 |
92 | }
93 | }
94 | public class Document {
95 | private static final Document INSTANCE = new Document();
96 |
97 | public static Document getInstance(){
98 | return INSTANCE;
99 | }
100 |
101 | }
102 |
103 | object Document {
104 |
105 | }
106 | public class ByteArrayUtils {
107 | public static String toHexString(byte[] data) {
108 |
109 | }
110 | }
111 |
112 | final var dummyData = new byte[10];
113 | final var hexValue = ByteArrayUtils.toHexString(dummyData);
114 | fun ByteArray.toHex() : String {
115 |
116 | }
117 |
118 | val dummyData = byteArrayOf()
119 | val hexValue = dummyData.toHex()
120 | public class Documment {
121 |
122 | class InnerClass {
123 |
124 | }
125 |
126 | }
127 | class Document {
128 | inner class InnerClass
129 | }
130 | public class Documment {
131 |
132 | public static class InnerClass {
133 |
134 | }
135 |
136 | }
137 | class Document {
138 |
139 | class InnerClass
140 |
141 | }
142 | public interface Printable {
143 | void print();
144 | }
145 |
146 | public class Document implements Printable {
147 | @Override
148 | public void print() {
149 |
150 | }
151 | }
152 | interface Printable {
153 | fun print()
154 | }
155 |
156 | class Document : Printable {
157 | override fun print() {
158 |
159 | }
160 | }
161 | Kotlin vs Java
public CompletableFuture<SomeOtherResult> loadAndCombine(String name1, String name2){
3 | loadImageAsync(name1)
4 | .thenAcceptBoth(loadImageAsync(name2)) ((one, two) -> {
5 | combineImages(one, two)
6 | )}
7 | }
8 | suspend fun loadAndCombine(name1: String, name2: String): Image =
9 | coroutineScope {
10 | val deferred1 = async { loadImage(name1) }
11 | val deferred2 = async { loadImage(name2) }
12 | combineImages(deferred1.await(), deferred2.await())
13 | }public <T> CompletableFuture<T> inTransaction(DatabaseFunction<T> fun) {
14 | return CompletableFuture
15 | .runAsync(() -> this.sendQuery("BEGIN"))
16 | .thenApply(ignored -> fun.execute(this))
17 | .thenApply(s -> {
18 | this.sendQuery("COMMIT");
19 | return s;
20 | }).exceptionally(throwable -> {
21 | this.sendQuery("ROLLBACK");
22 | return null;
23 | });
24 | }
25 | suspend fun <T> inTransaction(
26 | f: suspend (Connection) -> T): T {
27 | try {
28 | this.sendQuery("BEGIN")
29 | val result = f(this)
30 | this.sendQuery("COMMIT")
31 | return result
32 | } catch (e: Throwable) {
33 | this.sendQuery("ROLLBACK")
34 | throw e
35 | }
36 | }
37 |
38 | final var callables = Stream.of("Service A", "Service B", "Service C")
39 | .map(DummyService::new)
40 | .map(service -> (Callable<ContentDuration>) service::getContent)
41 | .collect(Collectors.toList());
42 |
43 | final var executor = Executors.newWorkStealingPool();
44 | final var results = executor.invokeAll(callables).stream()
45 | .map(
46 | future -> {
47 | try {
48 | return future.get();
49 | } catch (InterruptedException | ExecutionException e) {
50 | throw new RuntimeException(e);
51 | }
52 | }
53 | ).collect(Collectors.toList());
54 | val DummyService.asyncContent: Deferred<ContentDuration>
55 | get() = async(CommonPool) { content }
56 |
57 | var results = runBlocking {
58 | arrayOf("Service A", "Service B", "Service C")
59 | .map { DummyService(it) }
60 | .map { it.asyncContent }
61 | .map { it.await() }
62 | }
63 | Kotlin vs Java
private String value;
3 |
4 | public synchronized String getValue() {
5 | if (value == null) {
6 | value = "Something";
7 | }
8 | return value;
9 | }val lazyValue: String by lazy {
10 | "Something"
11 | }final ObjectMapper mapper = new ObjectMapper(); // jackson's objectmapper
12 | final MyPojo pojo = mapper.convertValue(map, MyPojo.class);
13 |
14 | // https://stackoverflow.com/a/16430704/2441104class User(val map: Map<String, Any?>) {
15 | val name: String by map
16 | val age: Int by map
17 | }public class PCLNewsAgency {
18 | private String news;
19 |
20 | private PropertyChangeSupport support;
21 |
22 | public PCLNewsAgency() {
23 | support = new PropertyChangeSupport(this);
24 | }
25 |
26 | public void addPropertyChangeListener(PropertyChangeListener pcl) {
27 | support.addPropertyChangeListener(pcl);
28 | }
29 |
30 | public void removePropertyChangeListener(PropertyChangeListener pcl) {
31 | support.removePropertyChangeListener(pcl);
32 | }
33 |
34 | public void setNews(String value) {
35 | support.firePropertyChange("news", this.news, value);
36 | this.news = value;
37 | }
38 | }class User {
39 | var name: String by Delegates.observable("") {
40 | prop, old, new ->
41 | println("$old -> $new")
42 | }
43 | } Kotlin vs Java
final var order = Sandwich()
3 | .type("toastie")
4 | .bread("white")
5 | .fillings(List.of("Cheese", "Ham"))
6 | .dressings(List.of("Pepper", "Worcestershire sauce"))
7 | .side("Crisps")
8 | .makeMeASandwich()
9 |
10 | System.out.println(ooSandwich.receipt())
11 |
12 | // https://www.kotlindays.com/2019/12/02/days-of-kotlin-a-dsl-for-everyone/index.htmlval dslSandwich = sandwich {
13 | with type "toasted"
14 | bread = "baguette"
15 |
16 | filling("cheese")
17 | filling("ham")
18 | filling("tomato")
19 |
20 | dressings {
21 | +"Basil"
22 | +"Pepper"
23 | }
24 |
25 | sideOrders {
26 | side("French Fries")
27 | }
28 |
29 | }
30 |
31 | println(dslSandwich.receipt())
32 |
33 | // https://www.kotlindays.com/2019/12/02/days-of-kotlin-a-dsl-for-everyone/index.htmlval result = html {
34 | head {
35 | title { +"HTML encoding with Kotlin" }
36 | }
37 | body {
38 | h1 { +"HTML encoding with Kotlin" }
39 | p {
40 | +"this format can be used as an"
41 | +"alternative markup to HTML"
42 | }
43 |
44 | // an element with attributes and text content
45 | a(href = "http://jetbrains.com/kotlin") { +"Kotlin" }
46 |
47 | // mixed content
48 | p {
49 | +"This is some"
50 | b { +"mixed" }
51 | +"text. For more see the"
52 | a(href = "http://jetbrains.com/kotlin") {
53 | +"Kotlin"
54 | }
55 | +"project"
56 | }
57 | p {
58 | +"some text"
59 | ul {
60 | for (i in 1..5)
61 | li { +"${i}*2 = ${i*2}" }
62 | }
63 | }
64 | }
65 | }final var act = this;
66 | final var layout = new LinearLayout(act);
67 | layout.setOrientation(LinearLayout.VERTICAL);
68 | final var name = new EditText(act);
69 | final var button = new Button(act);
70 | button.setText("Say Hello");
71 | button.setOnClickListener(
72 | () -> {
73 | Toast.makeText(act, "Hello, " + name.text + "!", Toast.LENGTH_SHORT)
74 | .show()
75 | }
76 | layout.addView(name);
77 | layout.addView(button);verticalLayout {
78 | val name = editText()
79 | button("Say Hello") {
80 | onClick { toast("Hello, ${name.text}!") }
81 | }
82 | }override fun onCreate(savedInstanceState: Bundle?) {
83 | super.onCreate(savedInstanceState)
84 |
85 | verticalLayout {
86 | padding = dip(30)
87 | editText {
88 | hint = "Name"
89 | textSize = 24f
90 | }
91 | editText {
92 | hint = "Password"
93 | textSize = 24f
94 | }
95 | button("Login") {
96 | textSize = 26f
97 | }
98 | }
99 | }application.install(Routing) {
100 | get("/") {
101 | call.respondText("Hello, World!")
102 | }
103 | get("/bye") {
104 | call.respondText("Good bye, World!")
105 | }
106 | }