How to Add as well as Subtract Two Matrices inwards Java

This is the instant programme inwards the serial of matrices related programming exercises inwards Java. In the final program, you lot receive got learned matrix multiplication too inwards this program, you lot volition larn how to perform improver too subtraction of 2 matrices inwards Java. We'll do methods to calculate both amount too departure of 2 matrices inwards Java program. In Mathematics, a matrix is a rectangular array amongst 2 dimensions known equally rows too columns. In Java, your tin plough over the sack utilisation a two-dimensional array to correspond a matrix because it too has 2 dimensions rows too columns. Since a 2D array is null but an array of the array inwards Java, the length of the outer array is equal to the lay out of rows too length of sub-array is equal to the lay out of columns.

For example, to correspond a 2x3 matrix inwards Java you lot demand to do a two-dimensional integer array amongst 2 rows too 3 columns e.g. int[][] matrix = novel int[2][3]. By default, each value inwards the two-dimensional array is populated amongst the default value for that information type i.e. null for an integer array.

In companionship to calculate amount of 2 matrices, you lot demand to loop through array too add together respective elements from each matrix e.g. if given matrices are X too Y too then improver of these matrices volition z[i][j] = x[i][j] + y[i][j]. For subtraction simply utilisation minus sign instead of plus sign.

How to add together 2 matrices inwards Java

In companionship to add together 2 matrices inwards maths, you lot simply demand to add together the  numbers inwards the matching positions e.g. lay out inwards the get-go row too column of the get-go matrix should live on added to the get-go lay out inwards the instant matrix equally well, equally shown inwards the next diagram:

That's why dimension of both matrices should live on same to perform improver e.g. both must receive got same row too same columns.

How to subtract 2 matrices inwards Java

In companionship to calculate the departure of 2 matrices, you lot simply demand to subtract numbers inwards the matching seat e.g. subtract the get-go lay out of the get-go matrix amongst the get-go lay out of the instant matrix. Actually, subtraction is null but the improver of a negative matrix e.g. to subtract matrix Influenza A virus subtype H5N1 too B, you lot perform improver of A + (-B).  Here is a overnice diagram which explains subtraction of matrices:

Now, let's encounter our programme to calculate amount too departure of 2 matrices inwards Java. Btw, if you lot are too interested inwards programming exercises, you lot could travail solving problems asked inwards diverse technical interviews e.g. Amazon  or Facebook or whatever startups. You tin plough over the sack detect a expert collection of those questions on Cracking the Coding Interview book. The sixth edition contains to a greater extent than than 189 problems too their solutions.

Java Program to add together too subtract 2 matrices inwards Java

Here is our consummate Java programme to perform improver too subtraction of 2 matrices. Unlike the final article where nosotros receive got created a degree called Matrix to correspond matrices inwards Java which had rows too columns too holds matrix information into a two-dimensional array, inwards this programme we'll perform improver too subtraction of matrices using static methods, which takes 2 matrices too render their amount too difference.

This is non actually an object-oriented approach but it's expert for such task. All programme is coded into a unmarried degree MatrixAdditionSubtractionDemo, which too has methods to perform improver too subtraction of matrices, a method to impress matrices into the dominance prompt too a method to read user input from the dominance prompt too populate the matrices. We are too using Scanner to read user input from the dominance prompt.

The code to examine the add() too subtract() method are within main() method, which creates 2 matrices inwards cast of two-dimensional array too locomote yesteryear it to these methods for calculating amount too difference.

import java.util.Scanner;  /*  * Java Program to add together too subtract 2 matrices.   * Influenza A virus subtype H5N1 matrix tin plough over the sack live on represented equally 2 dimensional array inwards Java  */ public class MatrixAdditionSubtractionDemo {    public static void main(String[] args) {      System.out         .println("Welcome to Java programme for calculating amount too departure of 2 matrices");      // nosotros demand a Scanner to read input from Console     Scanner scnr = new Scanner(System.in);      System.out.print("Please Enter lay out of rows: ");     int rows = scnr.nextInt();      System.out.print("Please Enter lay out of columns: ");     int columns = scnr.nextInt();     System.out.println();      System.out.println("Please Enter get-go matrix");     int[][] a = read(scnr, rows, columns);     System.out.println();      System.out.println("Please Enter instant matrix");     int[][] b = read(scnr, rows, columns);      scnr.close();          // adding 2 matrices     int[][] amount = add(a, b);      // subtracting 2 matrices     int[][] difference1 = subtract(a, b);     int[][] difference2 = subtract(b, a);      System.out.println("The amount of 2 matrices is: ");     System.out.println("A + B =");     printMatrix(sum);      System.out.println("The differnece of 2 matrices is: ");     System.out.println("A - B =");     printMatrix(difference1);      System.out.println("Subtraction of matrix inwards opposite order");     System.out.println("B - Influenza A virus subtype H5N1 =");     printMatrix(difference2);      scnr.close();   }    /**    * a method to populate a matrix yesteryear reading input from console inwards Java    *     * @param rows    * @param columns    * @return matrix filled yesteryear user input from console    */   public static int[][] read(Scanner s, int rows, int columns) {     int[][] result = new int[rows][columns];;     for (int i = 0; i < rows; i++) {       for (int j = 0; j < columns; j++) {         System.out.println("Enter value of [" + (i+1) + "][" + (j+1) +"]");         result[i][j] = s.nextInt();       }     }     return result;   }    /**    * Java Program to calculate amount of 2 matrices    *     * @param a    * @param b    * @return render amount of given matrices    */   public static int[][] add(int[][] a, int[][] b) {     int rows = a.length;     int columns = a[0].length;     int[][] result = new int[rows][columns];     for (int i = 0; i < rows; i++) {       for (int j = 0; j < columns; j++) {         result[i][j] = a[i][j] + b[i][j];       }     }     return result;   }    /**    * Java Program to calculate departure of 2 matrices    *     * @param a    * @param b    * @return departure of given matrix    */   public static int[][] subtract(int[][] a, int[][] b) {     int rows = a.length;     int columns = a[0].length;     int[][] result = new int[rows][columns];     for (int i = 0; i < rows; i++) {       for (int j = 0; j < columns; j++) {         result[i][j] = a[i][j] - b[i][j];       }     }     return result;   }    /**    * a Java method to impress upshot inwards matrix format.    *     * @param matrix    */   public static void printMatrix(int[][] matrix) {     int rows = matrix.length;     int columns = matrix[0].length;     for (int i = 0; i < rows; i++) {       for (int j = 0; j < columns; j++) {         System.out.print(matrix[i][j] + " ");       }       System.out.println();     }   } }  Output Welcome to Java programme for calculating amount and departure of 2 matrices Please Enter lay out of rows: 2 Please Enter lay out of columns: 2  Please Enter first matrix Enter value of [1][1] 1 Enter value of [1][2] 2 Enter value of [2][1] 3 Enter value of [2][2] 4  Please Enter instant matrix Enter value of [1][1] 5 Enter value of [1][2] 6 Enter value of [2][1] 7 Enter value of [2][2] 8 The amount of 2 matrices is:  Influenza A virus subtype H5N1 + B = 6 8  10 12  The departure of 2 matrices is:  Influenza A virus subtype H5N1 - B = -4 -4  -4 -4  Subtraction of matrix in opposite companionship B - Influenza A virus subtype H5N1 = 4 4  4 4

You tin plough over the sack encounter the amount too departure of matrices are correctly calculated equally per formula nosotros receive got discussed inwards the instant paragraph. One of the of import lessons I learned piece doing this practise was well-nigh Scanner class. Earlier, I was creating too closing Scanner on the read() method itself equally shown below:

public static int[][] read(int rows, int columns) {     int[][] result = new int[rows][columns];     Scanner s = new Scanner(System.in);     for (int i = 0; i < rows; i++) {       for (int j = 0; j < columns; j++) {         System.out.println("Enter value of [" + i + "][" + j +"]");         result[i][j] = s.nextInt();       }     }     s.close();     return result;   }

When I had this code, I was getting next Exception consistently piece reading instant matrices from dominance prompt:

Exception inwards thread "main" java.util.NoSuchElementException
at java.util.Scanner.throwFor(Scanner.java:862)
at java.util.Scanner.next(Scanner.java:1485)
at java.util.Scanner.nextInt(Scanner.java:2117)
at java.util.Scanner.nextInt(Scanner.java:2076)
at Pattern.read(Pattern.java:66)
at Pattern.main(Pattern.java:29)

This was coming because I was closing Scanner later reading get-go matrices too creating simply about other instance for reading instant matrices, this all await expert on code but Java doesn't allow that. Once you lot unopen the Scanner you lot cannot opened upwards it over again for the same stream, inwards our illustration nosotros are using System.in, which is an InputStream for reading information entered on the dominance prompt.

To solve this error, I am creating Scanner 1 time inwards the programme too supplying that to read method for reading run too 1 time I read both matrices from the dominance business I unopen the Scanner inwards the main() method itself. Even later working inwards Java for thence many years, I didn't know this detail. So, fifty-fifty a uncomplicated programme tin plough over the sack learn us simply about useful things :-)


That's all well-nigh how to add together too subtract 2 matrices inwards Java. If you lot are interested inwards to a greater extent than programming exercises you lot tin plough over the sack cheque out the postal service listed below or you lot tin plough over the sack too start solving problems from the "57 Challenges to Develop Your Coding Skills", a expert majority amongst lots of programs to ameliorate your programming skills.

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References
KhanAcademy - Adding too Subtracting Matrices

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