# Rotate matrix java – Java Program to Rotate the Matrix 180 degree

Rotate matrix java: In the previous article, we have discussed Java Program to Rotate the Matrix 90 degree

In this article we are going to see how we can write a program to rotate the matrix 180 degree in JAVA language.

## Java Program to Rotate the Matrix 180 degree

Rotate matrix 90 degrees java: A 3*3 Matrix is having 3 rows and 3 columns where this 3*3 represents the dimension of the matrix. Means there are 3*3 i.e. total 9 elements in a 3*3 Matrix.

Let’s understand it in more simpler way.

                   | A00   A01   A02 |
Matrix A =  | A10   A11   A12 |
| A20   A21   A22 | 3*3
• Matrix A represents a 3*3 matrix.
• A‘ represents the matrix element
• Aij‘ represents the matrix element at it’s matrix position/index.
• i‘ represents the row index
• j‘ represents the column index
• Means A00=Aij  where i=0 and j=0A01=aij where i=0 and j=1 and like this.
• Here we have started row value from 0 and column value from 0.

Let’s see different ways to rotate the Matrix 180 degree.

### Method-1: Java Program to Rotate the Matrix 180 degree By Static Initialization of Array Elements

Approach:

• Initialize and an array of size 3×3, with elements.
• Print the matrix elements from last to first.

Program:

public class matrix
{
public static void main(String args[])
{
// Initializing the 3X3 matrix i.e. 2D array
int arr[][] = {{19,25,32},{40,54,62},{70,20,60}};
int row, col;

System.out.print("The matrix elements are : ");
printMatrix(arr);

System.out.print("\nThe matrix elements after 180 degree rotation are : ");
printRotateMatrix(arr);
}
// Function to print the matrix
static void printMatrix(int arr[][])
{
int row, col;
// Loop to print the elements
for(row=0;row<3;row++)
{
// Used for formatting
System.out.print("\n");
for(col=0;col<3;col++)
{
System.out.print(arr[row][col]+" ");
}
}
}
// Function to print the rotatematrix
static void printRotateMatrix(int arr[][])
{
int row, col;
// Prints the elements from the last to first
for(row=2;row>=0;row--)
{
// Used for formatting
System.out.print("\n");
for(col=2;col>=0;col--)
{
System.out.print(arr[row][col]+" ");
}
}
}

}

Output:

The matrix elements are :
19 25 32
40 54 62
70 20 60
The matrix elements after 180 degree rotation are :
60 20 70
62 54 40
32 25 19

### Method-2: Java Program to Rotate the Matrix 180 degree By Dynamic Initialization of Array Elements

Approach:

• Declare one array of size 3×3.
• Take the array elements as input from the user.
• Find the transpose of the array, then reverse its elements. Again repeat the step and now we will get the matrix 180 degree rotated.
• Print the resultant matrix.

Program:

import java.util.Scanner;

public class matrix
{
public static void main(String args[])
{
//Scanner class object created to take input
Scanner scan = new Scanner(System.in);
// Initializing the 3X3 matrix i.e. 2D array
int arr[][] = new int[3][3];
int row, col ,oddCounter = 0, evenCounter = 0;
// Taking matrix1 input
System.out.println("Enter matrix elements : ");
for(row=0;row<3;row++)
for(col=0;col<3;col++)
arr[row][col] = scan.nextInt();

System.out.print("The matrix elements are :");
printMatrix(arr);
// Calls the transpose function inside the rotate array function
arr=rotateArr(trans(rotateArr(trans(arr))));
System.out.print("\nThe rotated matrix elements are : ");
printMatrix(arr);
}

// Method to find the transpose
static int[][] trans(int[][] mat)
{
int row, col, trans[][] = new int[3][3];
for(row=0;row<3;row++)
for(col=0;col<3;col++)
trans[row][col] = mat[col][row];

return trans;
}

// Reverses the array
static int[][] rotateArr(int arr[][])
{
for(int i=0;i<3;i++)
for(int j=0,k=2;j<k;j++,k--)
{
int temp = arr[j][i];
arr[j][i] = arr[k][i];
arr[k][i] = temp;
}
return arr;
}

// Method to print the matrix
static void printMatrix(int arr[][])
{
int row, col;
// Loop to print the elements
for(row=0;row<3;row++)
{
// Used for formatting
System.out.print("\n");
for(col=0;col<3;col++)
{
System.out.print(arr[row][col]+" ");
}
}
System.out.print("\n");
}

}


Output:

Enter matrix elements : 1 2 3 4 5 6 7 8 9
The matrix elements are :
1 2 3
4 5 6
7 8 9

The rotated matrix elements are :
9 8 7
6 5 4
3 2 1

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