├── Fibonacci series
├── First n prime numbers
├── Interface and inheritence
├── Largest and second largest number of an array
├── Maximum and minimum value in an array
├── Prime numbers: 1 to n
├── Removing duplicate elements of array
└── Reversing an array


/Fibonacci series:
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 1 | // Online Java Compiler
 2 | // Use this editor to write, compile and run your Java code online
 3 | import java.util.Arrays; 
 4 | class HelloWorld {
 5 |     public static void main(String[] args) {
 6 |         int n=500;
 7 |         int a=0;
 8 |         int b=1;
 9 |         int c=0;
10 |         while (c<n){
11 |             System.out.println(a);
12 |             int x=a+b;
13 |             a=b;
14 |             b=x;
15 |             c++;
16 |         }
17 |     }
18 | }
19 | 


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/First n prime numbers:
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 1 | package prime;
 2 | import java.util.*;
 3 | import java.lang.Math; 
 4 | public class prime {
 5 | 	 public static void main(String[]args)
 6 | 	    {
 7 | 		 	final long startTime = System.currentTimeMillis();
 8 | 	        int divisor,n=0,i=2;
 9 | 	        Scanner s = new Scanner(System.in);
10 | 	        int x=s.nextInt();
11 | 	        while(n<x){
12 | 	            divisor=1;  
13 | 	            int count=0;  
14 | 	            while(divisor<=(int)(Math.sqrt(i))){ 
15 | 	            	if(i%divisor==0)
16 | 	                	count++;  
17 | 	                divisor++;  
18 | 	            }  
19 | 	            if(count==1){ 
20 | 	                System.out.print(i + " ");  
21 | 	                n++;  
22 | 	            }  
23 | 	            i++;  
24 | 	        }
25 | 	        final long endTime = System.currentTimeMillis();
26 | 
27 | 	        System.out.println("\nTotal execution time: " + (endTime - startTime)/1000.0);
28 | 	    }
29 | 	}
30 | 


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/Interface and inheritence:
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 1 | interface Animals{
 2 |     public void nooflegs(int a);
 3 |     void theyeat();
 4 |     }
 5 | abstract class Herbivorous implements Animals{
 6 |     @Override
 7 |     public void theyeat(){
 8 |         System.out.println("Herbivores eat plants");
 9 |     }
10 | }
11 | abstract class Carnivorous implements Animals{
12 |     @Override
13 |     public void theyeat(){
14 |         System.out.println("Carnivores eat flesh");
15 |     }
16 | }
17 | abstract class Omnivorous implements Animals{
18 |     @Override
19 |     public void theyeat(){
20 |         System.out.println("Omnivores eat both plants and flesh");
21 |     }
22 | }
23 | class Elephant extends Herbivorous{
24 |     @Override
25 |     public void nooflegs(int a){
26 |         System.out.println("They have "+a+" legs."+"\n");
27 |         }
28 | }
29 | class Tiger extends Carnivorous{
30 |     @Override
31 |     public void nooflegs(int a){
32 |         System.out.println("They have "+a+" legs."+"\n");
33 |         }
34 |    
35 | } 
36 | class Bear extends Omnivorous{
37 |     @Override
38 |     public void nooflegs(int a){
39 |         System.out.println("They have "+a+" legs."+"\n");
40 |         }
41 |     
42 | }
43 | class Main {
44 |     public static void main(String[] args) {
45 |         Animals e = new Elephant();
46 |         e.theyeat();
47 |         e.nooflegs(4);
48 |         Animals t = new Tiger();
49 |         t.theyeat();
50 |         t.nooflegs(4);
51 |         Animals b = new Bear();
52 |         b.theyeat();
53 |         b.nooflegs(4);
54 |     }
55 | }
56 | 


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/Largest and second largest number of an array:
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 1 | public class Main {
 2 |     public static void main(String[] args) {
 3 |         int[] a = {1, 2, 5, 6, 8, 8,10,11,9,3};
 4 |         int large = -1;
 5 |         int slarge=-2;
 6 |         for (int i=0;i<a.length;i++) {
 7 |             if (a[i] > large)
 8 |             {
 9 |                 slarge = large;
10 |                 large = a[i];
11 |             }
12 |             else if (a[i]>slarge){
13 |                 if (a[i] == large) continue;
14 |                 slarge=a[i];
15 |             }
16 |             else{
17 |                 continue;
18 |             }
19 |         }
20 | 
21 |         System.out.println(large+"\n"+slarge);
22 |     }
23 | }
24 | 


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/Maximum and minimum value in an array:
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 1 | public class Main {
 2 |     public static void main(String[] args) {
 3 |         int[] a = {1, 2, 5, 6, 8};
 4 |         int large = a[0];
 5 |         int min =a[0];
 6 | 
 7 |         for (int i = 1; i < a.length; i++) {
 8 |             if (a[i] > large) 
 9 |             {
10 |                 large = a[i];
11 |             }
12 |             else min=a[i];
13 |         }
14 | 
15 |         System.out.println(large);
16 |         System.out.println(min);
17 |     }
18 | }
19 | 


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/Prime numbers: 1 to n:
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 1 | import java.util.*;
 2 | class HelloWorld {
 3 |     public static void main(String[] args) {
 4 |         Scanner s = new Scanner(System.in);
 5 |         System.out.println("Enter a number:");
 6 |         int n=s.nextInt();
 7 |         for(int i=2;i<=n;i++){
 8 |             int c=0;
 9 |             for(int j=1;j<=i;j++){
10 |                 if(i%j==0){
11 |                     c++;
12 |                 }
13 |             }
14 |             if(c==2){
15 |                 System.out.println(i+" ");
16 |             }
17 |     }
18 | }
19 | }
20 | 


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/Removing duplicate elements of array:
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 1 | import java.util.Arrays;
 2 | class HelloWorld {
 3 |     public static void main(String[] args) {
 4 |         int a[]={8,7,2,9,5,4,3,5,1};
 5 |         int b[]=new int[a.length];
 6 |         int t=0;
 7 |         int c = 0;
 8 |         Arrays.sort(a);
 9 |         for(int i=0;i<a.length;i++){
10 |             if(t!=a[i]){
11 |                 b[c]=a[i];
12 |                 t=a[i];
13 |                 c++;
14 |             }
15 |         }
16 |         System.out.println(Arrays.toString(b));
17 |     }
18 | }
19 | 


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/Reversing an array:
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 1 | public class Main
 2 | {
 3 |     public static void main(String[] args){
 4 |         int[] a = {9,3,8,6};
 5 |         int i=0,j=a.length-1;
 6 |             while (i < j)
 7 |             {   
 8 |                     int t = a[i];
 9 |                     a[i] = a[j];
10 |                     a[j] = t;
11 |                     i++;
12 |                     j--;
13 |                 }
14 |          for (i = 0; i < a.length; i++){
15 |             System.out.println(a[i]);
16 |         }
17 |     }
18 | }
19 | 


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