java program to print-sub-files-and-sub-directories-in-a-directory

package com.usr.files;

import java.io.File;

public class ListFiles {

     public static void main(String[] args) {

           File rootDir=new File("E:\\songs");

           listAllFiles(rootDir);

     }

     private static void listAllFiles(File file) {

           if(file.isDirectory()){

                System.out.println("Directory Name is:"+file.getName());

                for(int i=0;i<file.listFiles().length;i++){

                     listAllFiles(file.listFiles()[i]);

                }

                System.out.println("File Name is:"+file.getName());

           }

     }

}

Iterating a list in java

package com.usr.collections;

import java.util.ArrayList;

import java.util.Iterator;
import java.util.List;

public class IteratingArrayList {

   
    public static void main(String[] args) {
       
        List<String> list=new ArrayList<String>();
        list.add("one");
        list.add("two");
        list.add("three");
        list.add("four");
        list.add("five");
        System.out.println("Iterating with for loop:");
       
        for(int i=0;i<list.size();i++){
           
            System.out.println(list.get(i));
           
        }
       
       
        System.out.println("Iterating with for each loop:");
       
        for(String list1:list){
            System.out.println(list1);
        }
       
       
        System.out.println("using while loop:");
        int j=0;
        while(j<list.size()){
            System.out.println(list.get(j));
            j++;
        }
       
       
        System.out.println("using iterator:");
        Iterator<String> itr=list.iterator();
        while(itr.hasNext()){
            System.out.println(itr.next());
        }

    }

}

java program to print prime numbers

package com.usr;

import java.util.Scanner;

public class PrimeNumbers {

   
    public static void main(String[] args) {
       
          Scanner sc=new Scanner(System.in);
          System.out.println("Enter the number upto where ypu need to print prime numbers:");
          int number=sc.nextInt();
          int i,j,k;
          for(i=1;i<number;i++){
              for(j=2;j<i;j++){
                  k=i%j;
                  if(k==0){
                      break;
                  }
              }
              if(i==j){
                  System.out.println(""+i);
              }
          }
        
    }

}

java program to check palindrome string

package com.usr;

import java.util.Scanner;

public class PalindromeString {

    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        System.out.println("Enter the string :");
        String original=sc.next();
        int length=original.length();
        String reverse="";
        for(int i=length-1;i>=0;i--){
            reverse=reverse+original.charAt(i);
        }
        if(original.equals(reverse)){
           
            System.out.println("string is palindrome");
        }
        else{
            System.out.println("string is not a palindrome and the reverse of string is:"+reverse);
        }

    }

}