In this article, I have provided list of various usefule and beginners java programming example with output, like simple hello world program, adding two numbers, printing pyramid in java etc., which can be helpful for beginners to understand the syntax and logic of Java programming, so here is the list.

Java Hello world program

public class HelloWorld{

	public static void main(String args[]){
		System.out.println("Hello World");
	}
}

Output:

Hello World
  • class keyword is used to declare a class in java
  • public keyword is an access modifier which represents visibility, it means this function is visible to all.
  • static is a keyword, used to make a static method. The advantage of static method is that there is no need to create object to invoke the static method. The main()
  • method here is called by JVM, without creating any object for class.
  • void is the return type of the method, it means this method will not return anything.
  • Main: main() method is the most important method in a Java program. It represents startup of the program.
  • String[] args is used for command line arguments.
  • System.out.println() is used to print statements on the console.

Read: Hello World program in Java (Your first java program)

Addition of two numbers in java

package add;

import java.util.Scanner;

public class Addition {
	public static void main(String[] args) {
	   Scanner input = new Scanner(System.in);
	  
	   System.out.println("Enter two numbers to add: ");
	   int num1 = input.nextInt();
	   int num2 = input.nextInt();
	   
	   System.out.println(num1+num2);
	}
}

Output:

Enter two numbers to add: 
5 20
25

add-two-number-in-java-program-example-min.png

In the above code, we are asking user to input two numbers using Scanner class and saving values as num1 & num2, then adding it.

Leap year program in Java

import java.util.Scanner;
public class Lear_year {
 public static void main(String args[]) {
  Scanner s = new Scanner(System.in);
  System.out.print("Enter any year:");
  
  int year = s.nextInt();
  
  boolean flag = false;
  
  if (year % 400 == 0) {
   flag = true;
  } else if (year % 100 == 0) {
   flag = false;
  } else if (year % 4 == 0) {
   flag = true;
  } else {
   flag = false;
  }
  if (flag) {
   System.out.println("Year " + year + " is a Leap Year");
  } else {
   System.out.println("Year " + year + " is not a Leap Year");
  }
 }
}

Output:

Enter any year:2015
Year 2015 is not a Leap Year

Enter any year:2016
Year 2016 is a Leap Year

In the above program, we are checking if a number is leap year of not, by dividing it, by 400, 100 and 4 using % , as it gives remainder, if it remainder value then it is not a leap year.

java-leap-year-program-min.png

Armstrong number program in java

package com.armstrong;

import java.util.Scanner;

public class ArmstrongNumberCheck {
	public static void main(String args[])
	   {
	      int number, sum = 0;
	 
	      Scanner in = new Scanner(System.in);
	      System.out.println("Enter a number to check if it is an armstrong number");      
	      number = in.nextInt();	 	      
	 
	     /* Converting Integer to String. It'll help to find number of
        digits in the Integer by using length() */
	      String temp = number + "";
	      //get number length
	      int numLength = temp.length();
	      //copy the main Number in a variable
	      int numCopy = number;	     
	      
	      //loop all the numbers until remainder is 0
	      while(numCopy != 0 ){
		       int remainder = numCopy % 10;
		       // using Math.pow to get digit raised to the power
		       // total number of digits
		       sum = sum + (int)Math.pow(remainder, numLength);
		       numCopy = numCopy/10;
	      }
	      
	      System.out.println("sum is " + sum );
	 
	      if (number == sum )
	      {
	         System.out.println( number + " is an armstrong number.");
	      }
	      else
	      {
	         System.out.println(number+ " is not an armstrong number.");  
	      }
	      in.close();
	      
	   }
}

Output:

Enter a number to check if it is an armstrong number
9474
sum is 9474
9474 is an armstrong number.

Enter a number to check if it is an armstrong number
121
sum is 10
121 is not an armstrong number.

Enter a number to check if it is an armstrong number
371
sum is 371
371 is an armstrong number.

Print prime number from 1 to 100 in Java

public class PrimeNumber {

    public static void main(String[] args) {

        int p = 0;

        System.out.println("prime no are :");

        for (int i = 2; i <= 100; i++)
        {
            for (int j = 2; j <= 100; j++)
            {
                if ((i % j) == 0)
                {
                    if (i != j)
                        break;
                    else
                    {
                        p = i;
                        System.out.println(p);
                    }
                }
            }
        }
    }
}

Output:

prime no are :
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97

Fibonacci Series program in Java

package com.fib;

import java.util.Scanner;

public class fibonacciExample {
	public static void main(String[] args) {
		   Scanner input = new Scanner(System.in);
		  
		   System.out.println("Enter the number to limit Fibonacci series: ");
		   int num = input.nextInt();
		   //loop till the last count
		   for(int i = 1; i <= num; i++){
			   //call Fibonacci function to print sum of last two numbers
		      System.out.print(printFibonacci(i) + " ");
		   }
		   input.close();
		 }
		 
		 
		 // recursion function
		 private static int printFibonacci(int CurrentNumber){
		  //exit condition 
		  if(CurrentNumber == 1 || CurrentNumber == 2){
		   return 1;
		  }
		  return printFibonacci(CurrentNumber - 1) + printFibonacci(CurrentNumber - 2);
		 }

}

Output:

Enter how many numbers are needed in Fibonacci series: 
10
1 1 2 3 5 8 13 21 34 55

fibonacci-series-program-in-java-min.png

In the above program, we are using a recursion function to print fibonacci series, basically, we ask user about how many number ( for loop) fibonacci series needs to be printed and call fibonacci function for that number of times, each time we add "currentNumber-1" and "CurrentNumber-2" value, and return it to print.

Java program to reverse a string

class ReverseString
{
    public static void main(String[] args)
    {
        String input = "qawithexperts";
 
        // getBytes() method to convert string 
        // into bytes[].
        byte [] strAsByteArray = input.getBytes();
 
        //create a new byte array for storing results
        byte [] result = 
                   new byte [strAsByteArray.length];
 
        // Store result in reverse order into the
        // result byte[]
        for (int i = 0; i<strAsByteArray.length; i++)
            result[i] = 
             strAsByteArray[strAsByteArray.length-i-1];
 
        //print the new byte array as string
        System.out.println(new String(result));
    }
}

Output:

strepxehtiwaq

reverse-string-using-java-program.png

In the above program, we are revesring the string by traversing the string from backward and saving that string in new byte array from last to first character one by one using for loop in reverse, then printing it.

Printing Right angled * pattern triangle in Java

import java.io.*;

// Java code to demonstrate star pyramid pattern
public class JavaWithQAWithExperts
{
	// Function to demonstrate printing pattern
	public static void printStars(int n)
	{
                //Declare two vairables
		int i, j;

		// outer loop to handle number of rows
		// n in this case, you can provide static values like 5 for printing 5 rows
		for(i=0; i<n; i++)
		{

			// inner loop to handle number of columns			
			for(j=0; j<=i; j++)
			{
				// printing stars
				System.out.print("* ");
			}

			// just to break line, after loop for each row is completed
			System.out.println(); 
		}
}

	// Main function
	public static void main(String args[])
	{
		int n = 5;
                //Call the printStars function by passing integer value, here it is 5
		printStars(n);
	}
}

Output:

* 
* * 
* * * 
* * * * 
* * * * *

When we are creating a pyramid, we need to need two loops( easy way, we can do it with one loop also), one for printing the "*" or you can say numbers, another to start loop again for next row(once first loop is over, call the outer loop to print next line). So, basically

Printing Equilateral triangle in Java

import java.io.*;

// Java code to demonstrate star pattern
public class JavaWithQAWithExperts
{
	//Main function to print triangle
	public static void printTriangle(int n)
	{
		// k= number of spaces
		int k = 2*n - 2,i,j;

		// outer loop to handle number of rows
		
		for (i=0; i<n; i++)
		{

			// inner loop to handle number spaces
			// values changing acc. to requirement
			for (j=0; j<k; j++)
			{
				// printing spaces
				System.out.print(" ");
			}

			// decrementing k after each loop
			k = k - 1;

			// inner loop to handle number of columns
			
			for (j=0; j<=i; j++ )
			{
				// printing stars
				System.out.print("* ");
			}

			// ending line after each row
			System.out.println();
		}
	}
	
	// Calling Function
	public static void main(String args[])
	{
		int n = 5; //number of rows
                 //call function to print triangle
		printTriagle(n);
	}
}

Output

        * 
       * * 
      * * * 
     * * * * 
    * * * * * 

In the above code, we are using K variable to print spaces but this time we are decrementing it by 1,i.e, k= k-1 , after each loop of printing spaces get's over, so basically logic is same as per the 2nd code, but changing it a little bit it generates equivalent triangle.

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