Here are the 13 java programs for you to practice and hone your programming skills with java.

Basic program in Java
Java Programs on numbers
Programs on strings in Java
Advanced Java Programs
Programs on Arrays in Java
Recursion Programs In Java
Searching/Sorting Program In Java

Java Programs on numbers

Fibonacci Series Program In Java(without recursion)
Factorial Program In Java
Java Program to check for leap year

Programs On Strings In Java

Java Program To Reverse A String
Java Program For Sorting A String
Java Program for counting Consonants and Vowels in a String

Programs On Arrays In Java

Java Program for printing duplicates from an Array
Java program to sort elements in Array
Java program for reversing elements of an Array

Recursion Programs in Java

Java program to check for palindrome(with recursion)
Java program to reverse a string (with recursion)

Searching/Sorting Program In Java

Java program to implement the bubble sort algorithm
Java program to implement the binary search algorithm

Java Programs on numbers

Fibonacci Series Program In Java(without recursion)

import java.util.Scanner;

 

public class Fibonacci{

  public static void main(String args[]) {

    System.out.println(“How many Fibonacci terms do you want? “);

    // creating a scanner object

    Scanner scn = new Scanner(System.in);

    int counter = scn.nextInt(); // taking the input with scanner

 

    int a = 0;

    int b = 1;

    int c, k;

    System.out.print(a + ” ” + b); // fib value for 0 and 1

 

    for (k = 2; k < counter; ++k) // looping starts from 2

    {

      c = a + b;

      System.out.print(” ” + c);

      a = b;

      b = c;

    }

    scn.close();

  }

}

Output for the above program

How many Fibonacci terms do you want? 7 

0 1 1 2 3 5 8

Factorial Program In Java

import java.util.Scanner;

 

public class Main {

 public static void main(String args[]) {

   System.out.println(“Find the factorial of: “);

   // creating a scanner object

   Scanner scn = new Scanner(System.in);

   int number = scn.nextInt(); // taking the input with scanner

 

   int k, fact = 1; // first factorial value

 

   for (k = 1; k <= number; k++) {

     fact = fact * k;

   }

   System.out.println(“Factorial of ” + number + ” is: ” + fact);

   scn.close();

 }

}

Output for the above program

Find the factorial of: 

6

Factorial of 6 is: 720

Java Program to check for leap year

import java.util.Scanner;

 

public class Leap{

 

 public static void main(String[] args) {

   System.out.println(“Check leap year for: “);

   Scanner scn = new Scanner(System.in); // scanner object

   int yr = scn.nextInt(); // taking the input with scanner

   boolean leap_yr = false;

 

   if (yr % 4 == 0) {

     if (yr % 100 == 0) {

       // if yr is divisible by 400 it is a leap year

       if (yr % 400 == 0)

         leap_yr = true;

       else

         leap_yr = false;

     } else

       leap_yr = true;

   } else

     leap_yr = false;

 

   if (leap_yr)

     System.out.println(yr + ” is a leap year.”);

   else

     System.out.println(yr + ” is not a leap year.”);

   scn.close();

 }

}

Output 1 for the above program 

Check leap year for: 

1990

1990 is not a leap yr.

Output 2 for the above program 

Check leap year for: 

2020

2020 is a leap year.

Programs On Strings In Java

Java Program To Reverse A String

import java.util.Scanner;

 

public class Main {

 public static void main(String[] args) {

   System.out.println(“Reversed string for: “);

   Scanner scn = new Scanner(System.in); // scanner object

   String str = scn.nextLine(); // taking the input with scanner

   // For storing the reverse of the given string

   String reversedStr = “”;

 

   // Iterate string from last and add each character to reversedStr

   for (int s = str.length() – 1; s >= 0; s–) {

     reversedStr = reversedStr + str.charAt(s);

   }

 

   System.out.println(“Original string: ” + str);

   //reverse of the given string

   System.out.println(“Reversed string: ” + reversedStr);

   scn.close();

 }

}

Output for the above program

Reversed string for: year

Original string: year

Reversed string: raey

Java Program For Sorting A String

import java.util.Arrays;

import java.util.Scanner;

public class Main {

 public static void main(String[] args) {

   // creating an object of Scanner class for input

   Scanner scn = new Scanner(System.in);

   // taking input from users with scn

   System.out.print(“First String: “);

   String str_1 = scn.nextLine();

   System.out.print(“Second String: “);

   String str_2 = scn.nextLine();

   if(str_1.length() == str_2.length()) {

     // converting strings to arrays

     char[] arr_1 = str_1.toCharArray();

     char[] arr_2 = str_2.toCharArray();

     // sorting the arrays

     Arrays.sort(arr_1);

     Arrays.sort(arr_2);

     boolean ang = Arrays.equals(arr_1, arr_2);

     if(ang) {

       System.out.println(“The strings are valid anagram.”);

     }

     else {

       System.out.println(“The strings are not valid anagram.”);

     }

   }

   else{

     System.out.println(“The strings are not valid anagrams”);

   }

   scn.close();

 }

}

Output for the above program

First String: reader

Second String: read

The strings are not valid anagrams

Java Program For Counting Consonants And Vowels In A String

import java.util.Scanner;

 

public class Main {

 public static void main(String[] args) {

 

   int vowel = 0;

   int consonant = 0;

   // creating an object of Scanner for input

   Scanner scn = new Scanner(System.in);

   // taking input from users with scn

   System.out.print(“Your String: “);

   String strng = scn.nextLine();

 

   input = input.toLowerCase();

 

   for (int s = 0; s < strng.length(); s++) 

{

     if (strng.charAt(s) == ‘a’ || strng.charAt(s) == ‘e’ || strng.charAt(s) == ‘i’ || strng.charAt(s) == ‘o’

         || strng.charAt(s) == ‘u’) {

       // Increments the vowel counter

       vowel++;

     } else if (strng.charAt(s) >= ‘a’ && strng.charAt(s) <= ‘z’) {

       consonant++;

     }

   }

   System.out.println(“vowels: ” + vowel);

   System.out.println(“consonants: ” + consonant);

   scn.close();

 }

}

Output for the above program

Your String: the simplest string ever

Number of vowels: 6

Number of consonants: 15

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Programs On Arrays In Java

Java Program for printing duplicates from an Array

public class Duplicate{

 public static void main(String[] args) {

 

   int[] array = new int[] { 1, 1, 2, 3, 5, 2, 3, 5, 7 };

 

   System.out.println(“Founded these duplicate elements: “);

   for (int r = 0; r < array.length; r++) {

     for (int c = r + 1; c < array.length; c++) {

       if (array[r] == array[c])

         System.out.println(array[c]);

     }

   }

 }

}

Output for the above program

Founded these duplicate elements: 

1

2

3

5

Java program to sort elements in Array

public class Sort {

 public static void main(String[] args) {

 

   // Initialize the original array

   int[] array = new int[] { 4,6,7,1,2,4 };

   int tmp = 0;

   int len = array.length

 

   // Sort the array in ascending order

   for (int h = 0; h < len; h++) {

     for (int c = h + 1; c < len; c++) {

       if (array[h] > array[c]) {

         tmp = array[k];

         array[h] = array[c];

         array[c] = tmp;

       }

     }

   }

 

   System.out.println();

 

   // Elements of array after sort

   System.out.println(“Array after sorting: “);

   for (int h = 0; h < len; h++) {

     System.out.print(array[h] + ” “);

   }

 }

}

Output for the above program

Sorted elements: 

1 2 4 4 6 7

Java program for reversing elements of an Array

public class Main {

 public static void main(String[] args) {

   // Initialize array

   int[] arr = new int[] { 1, 1, 2, 3, 5 };

   len = arr.length

   System.out.println(“reversed array : “);

   // Looping through array from last

   for (int h = len – 1; h >= 0; h–) {

     System.out.print(arr[h] + ” “);

   }

 }

}

Output for the above program

reversed array : 

5 3 2 1 1 

Recursion Programs in Java

Java program to check for palindrome(with recursion)

class Palindrome {

 static int pal(int num, int tmp) {

   // base case

   if (num == 0)

     return tmp;

   tmp = tmp * 10 + num % 10;

 

   return pal(num / 10, tmp);

 }

 

 public static void main(String[] args) {

   int num = 1221;

   int tmp = pal(num, 0);

 

   if (tmp == num)

     System.out.println(“A palindrome number”);

   else

     System.out.println(“Not a palindrome number”);

 }

}

Output for the above program

A palindrome number

Java program to reverse a string (with recursion)

public class ReversedString {

   public String reverse(String strng){

   

      if(strng.isEmpty()){

         return strng;

      } else {

         return reverse(strng.substring(1))+strng.charAt(0);

      }

   }

   public static void main(String[] args) {

      ReversedString obj = new ReversedString();

      String result = obj.reverse(“Fita Academy”);

      System.out.println(result);

   }

}

Output for the above program

ymedacA atiF

Java program to implement bubble sort algorithm

import java.util.Arrays;

import java.util.Scanner;

class Main {

// method to perform bubble sort

void bubble(int arry[]) {

  int len = arry.length;

  // for getting elements from array arry

  for (int m = 0; m < len – 1; m++) {

    // for comparison

    for (int n = 0; n < len – m – 1; n++) {

      // comparing with the next element

      if (arry[n + 1] < arry[n]) {

        // performing swap

        int temp = arry[n];

        arry[n] = arry[n + 1];

        arry[n + 1] = temp;

      }

    }

  }

}

// driver method

public static void main(String args[]) {

  int[] array = { -2, 4, -6, 0, 9 };

  // creating an object of Main

  Main bs = new Main();

  bs.bubble(array);

  System.out.println(“Sorted array:”);

  // for converting int to string

  System.out.println(Arrays.toString(array));

}

}

Output for the above program

Sorted array:

[-6, -2, 0, 4, 9]

Java program to implement the binary search algorithm

import java.util.Scanner;

import java.util.Arrays;

 

class Main {

 int binarySearch(int arr[], int element, int lower, int higher) {

 

   while (lower <= higher) {

 

     // get index of middle element

     int middle = lower + (higher – lower) / 2;

 

     // if element to be searched is middle

     if (arr[middle] == element)

       return middle;

 

     // if element is lesser than middle

     // search on the left of middle

     if (arr[middle] < element)

       lower = middle + 1;

 

     // if element is greater than middle

     // search on the right of middle

     else

       higher = middle – 1;

   }

 

   return -1;

 }

 

 public static void main(String args[]) {

 

   // create an object of the Main class

   Main obj = new Main();

 

   int[] arr = { 3, 4, 5, 6, 7, 8, 9 };

   int n = arr.length;

 

   // creating a scanner object to take input from a user

   Scanner scn = new Scanner(System.in);

 

   System.out.println(“Element to be searched for:”);

 

   int element = scn.nextInt();

   scn.close();

 

   int res = obj.binarySearch(arr, element, 0, n – 1);

   if (res == -1)

     System.out.println(“Element not found in the array”);

   else

     System.out.println(“Element found in array at index ” + res);

 }

}

Output for the above program

Element to be searched for:

5

Element found in array at index 2

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