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FillZero.java

import java.util.*;

public class FillZero {
    /**
     * user enters the matrix and program sets zeros
     * @param args
     */
	public static void main(String[] args) {
		Scanner input = new Scanner(System.in);
		
		while(true){
		   System.out.println("Please enter # row of your matrix: ");
		   int row = input.nextInt();
		   System.out.println("Please enter # column of your matrix: ");
		   int col = input.nextInt();
		   
		   int[][] matr = new int[row][col];
		   System.out.println("Please enter the matrix by rows: ");
		   
		   for(int i=0; i<row; i++){
			   for(int j=0; j<col; j++){
				  matr[i][j] = input.nextInt();
			   }
	       }
		   
		   writeZero(matr, row, col);
		   System.out.println("The new matrix is: ");
		   printMatrix(matr, row, col);
		   
		   System.out.println("continue?(y/n): ");
		   if(input.next().equals("n")){
			   System.exit(0);
		   } 		
		}

	}
	
	/**
	 * set zero for rows and columns
	 * @param matr
	 * @param row
	 * @param col
	 */
	public static void writeZero(int[][] matr, int row, int col){
		//lists to store the row/column number where zeros lie
		ArrayList<Integer> zeroRow = new ArrayList<Integer>();
		ArrayList<Integer> zeroCol = new ArrayList<Integer>();
		for(int i=0; i<row; i++){
			for(int j=0; j<col; j++){
				if(matr[i][j] == 0){
					zeroRow.add(i);
					zeroCol.add(j);
				}
			}
		}
		
		int[] newRow = new int[col];
	    
		//set zeros
		for(int i: zeroRow){
			matr[i] = newRow;
		}
		for(int j: zeroCol){
		   for(int k=0; k<row; k++){
			   matr[k][j] = 0;
		   }
		}	
	}
	
	/**
	 * print the matrix
	 * @param matr
	 * @param row
	 * @param col
	 */
	public static void printMatrix(int[][] matr, int row, int col){
		for(int i=0; i<row; i++){
			for(int j=0; j<col; j++){
				System.out.printf("%-5d", matr[i][j]);
			}
			System.out.println();
		}
	}

}