Java program to add two matrices

This java program add two matrices. You can add matrices of any order.

Java programming source code

import java.util.Scanner;
 
class AddTwoMatrix
{
   public static void main(String args[])
   {
      int m, n, c, d;
      Scanner in = new Scanner(System.in);
 
      System.out.println("Enter the number of rows and columns of matrix");
      m = in.nextInt();
      n  = in.nextInt();
 
      int first[][] = new int[m][n];
      int second[][] = new int[m][n];
      int sum[][] = new int[m][n];
 
      System.out.println("Enter the elements of first matrix");
 
      for (  c = 0 ; c < m ; c++ )
         for ( d = 0 ; d < n ; d++ )
            first[c][d] = in.nextInt();
 
      System.out.println("Enter the elements of second matrix");
 
      for ( c = 0 ; c < m ; c++ )
         for ( d = 0 ; d < n ; d++ )
            second[c][d] = in.nextInt();
 
      for ( c = 0 ; c < m ; c++ )
         for ( d = 0 ; d < n ; d++ )
             sum[c][d] = first[c][d] + second[c][d];  //replace '+' with '-' to subtract matrices
 
      System.out.println("Sum of entered matrices:-");
 
      for ( c = 0 ; c < m ; c++ )
      {
         for ( d = 0 ; d < n ; d++ )
            System.out.print(sum[c][d]+"\t");
 
         System.out.println();
      }
   }
}

Output of program:



This code adds two matrix, you can modify it to add any number of matrices. You can create a Matrix class and create it's objects and then create an add method which sum the objects, then you can add any number of matrices by repeatedly calling the method using a loop.

Java program to reverse number

This program prints reverse of a number i.e. if the input is 951 then output will be 159.

Java programming source code

import java.util.Scanner;
 
class ReverseNumber
{
   public static void main(String args[])
   {
      int n, reverse = 0;
 
      System.out.println("Enter the number to reverse");
      Scanner in = new Scanner(System.in);
      n = in.nextInt();
 
      while( n != 0 )
      {
          reverse = reverse * 10;
          reverse = reverse + n%10;
          n = n/10;
      }
 
      System.out.println("Reverse of entered number is "+reverse);
   }
}

Output of program:



You can also reverse or invert a number using recursion. You can use this code to check if a number is palindrome or not, if the reverse of an integer is equal to integer then it's a palindrome number else not.

 

Java program to get ip address

This program prints IP or internet protocol address of your computer system. InetAddress class of java.net package is used, getLocalHost method returns InetAddress object which represents local host.

Java programming source code

import java.net.InetAddress;
 
class IPAddress
{
   public static void main(String args[]) throws Exception
   {
      System.out.println(InetAddress.getLocalHost());
   }
}

Output of program:



Output of code prints computer name/ IP address of computer. Java has a very vast Networking API and can be used to develop network applications.

Java program to perform garbage collection

This program performs garbage collection. Free memory in java virtual machine is printed and then garbage collection is done using gc method of RunTime class, freeMemory method returns amount of free memory in jvm, getRunTime method is used to get reference of current RunTime object.

Java programming source code

import java.util.*;
 
class GarbageCollection
{
   public static void main(String s[]) throws Exception
   {
      Runtime rs =  Runtime.getRuntime();
      System.out.println("Free memory in JVM before Garbage Collection = "+rs.freeMemory());
      rs.gc();
      System.out.println("Free memory in JVM after Garbage Collection = "+rs.freeMemory());
   }
}

Output of program:




Obviously the amount of available after garbage collection will be different on your computer. Numbers are not important, what is important is that amount of memory available is more than before. You can use this code in your program or projects which uses large amount of memory or where frequently new objects are created but are required for a short span of time.