Question

Question:

matrix m1 = new matrix(); // should produce a matrix of 3*3

matrix m2 = new matrix(5,4); //5*4

matrix m3 = new matrix(m2); //5*4

What should be there in the copy constructor to make a new matrix m3 of the same order as of m2?

 public class matrix {

    int a[ ][ ];

       matrix(){
        a = new int[3][3];  
      }

     matrix(int x, int y){
        a= new int [x][y];      
      }

     matrix (matrix b1){        
      //how to use value of x and y here....
      }

void show(){

        System.out.println(a.length);
        for(int i=0;i<a.length;i++){
            System.out.print(a[i].length);      
            }
        } 
     }




public class matrixtest { 

public static void main(String [ ] args){   

       matrix a = new matrix();     
       matrix b = new matrix(5,4);  
       matrix c  = new matrix (b);  
       a.show(); 

       b.show(); 

       c.show(); 
   } 

}

NOTE: You can not use any extra instance variable except the array a.

Accepted answer: @Chankey: this(b1.a.length,b1.a[0].length); – John

Answer 1

Store the number of rows, and the number of columns in the matrix class, and create getters for them.

public class Matrix {
    int[][] a;
    int rowNum;
    int colNum;

    //...
    public Matrix(Matrix b) {
       a=new int[b.getRowNum()][b.getColNum()];
       this.rowNum = b.getRowNum();
       this.colNum = b.getColNum();
    }

    public int getRowNum() {
       return this.rowNum;
    }


}