• Do some more difficult interpretation of Java code.
• Write code using 2D arrays

public class Matrix {

    int[][] data;
     
    Matrix( int[][] matrixData ){
        this.data = new int[matrixData.length][matrixData[0].length];
        for( int row = 0; row < matrixData.length; ++row){
               
            for( int col = 0; col < matrixData[0].length; ++col){
                this.data[row][col] = matrixData[row][col];
            }
        }
          
    }
     
    public int getRows(){
        return this.data.length;
    }
     
    public int getColumns(){
        return this.data[0].length; //we can assume that 2D array is rectangular
    }
     
    public int getDataAt( int row, int column ){
        return this.data[row][column];
    }
     
    public int[][] addMatrix( Matrix otherMatrix ) {

        if( this.getRows() != otherMatrix.getRows() || this.getColumns() != otherMatrix.getColumns() ){
            System.out.println("Matrices must be same size");
            System.out.println( "this Matrix: "+ this.getRows() + " rows "+ this.getColumns() + " columns");
            System.out.println( "otherMatrix: "+ otherMatrix.getRows() + " rows, "+ otherMatrix.getColumns()+ " columns");
            System.exit(-1);
        }

        int[][] additionData = new int[this.getRows()][this.getColumns()];

        for( int row = 0; row < this.getRows(); ++row ){

            for( int col = 0; col < this.getColumns(); ++col){
                additionData[row][col] = this.getDataAt(row, col) + otherMatrix.getDataAt(row, col);
            }
        }

        return additionData;
    }

    public void transpose(){

        int[][] transposeData = new int[this.getColumns()][this.getRows()];
        for( int row = 0; row< this.getRows(); ++row){
            for( int col = 0; col < this.getColumns(); ++col){
                transposeData[col][row] = this.getDataAt(row, col);
            }
        }
        this.data = transposeData;
    }

    public String toString(){

        String output = "";
        for( int row = 0; row < this.getRows(); ++row ){

            for( int col = 0; col < this.getColumns(); ++col){
                output += this.getDataAt(row, col) + ", ";
            }
            output += "\n";
        }
        return output;
    }

    public static void main(String[] args) {

        int[][] matrixAData = { {1, 2},  
                            	{3, 4}, 
                            	{5, 6} };
                            

        int[][] matrixBData = { {7,  8 },
                           	{9,  10},
                            	{11, 12} };

        Matrix matrixA = new Matrix( matrixAData );
        Matrix matrixB = new Matrix( matrixBData );

        Matrix additionMatrix = new Matrix( matrixA.addMatrix( matrixB ) );

        System.out.println( matrixA.toString() );
        System.out.println( matrixB.toString() );
        System.out.println( additionMatrix.toString() );

        matrixA.transpose();
        System.out.println( matrixA.toString() );

        Matrix transAddMatrix = new Matrix( matrixA.addMatrix( matrixB ) );
        System.out.println( transAddMatrix.toString() );
    }
}

1. Make a new R22 project and copy Matrix.java (from above) into it.
2. Write a method with the following signature:
   
   // returns true if this matrix is an identity matrix
public boolean isIdentity( ){ }