Q1_7.java

public class Q1_7 {
	public static void main(String args[]) {
		int a[][] = {
		        {0, 2, 0, 4},
		        {5, 6, 7, 8},
		        {9, 10, 0, 12},
		        {13, 14, 15, 16}};
		 process(a);  
		 for(int[] x :a){
			 for(int integer :x)
				 System.out.print(integer+"  ");
			 System.out.println("  ");
		 }

	}

	public static void process(int[][] matrix) {
		boolean firstRow = false;
		boolean firstCol = false;

		for (int i = 0; i < matrix.length; i++) {
			if (matrix[i][0] == 0){
				firstCol = true;
				break;
			}	
		}
		for (int i = 0; i < matrix[0].length; i++) {
			if (matrix[0][i] == 0){
				firstRow = true;
				break;
			}				
		}
		
		for (int i = 0; i < matrix.length; i++) {
			for (int j = 0; j < matrix[0].length; j++) {
				if (matrix[i][j] == 0) {
					matrix[0][j] = 0;
					matrix[i][0] = 0;
				}
			}
		}
                // check from 1 to ensure not to change the first row
		for (int i = 1; i < matrix.length; i++) {
			if (matrix[i][0] == 0) {
				for (int j = 1; j < matrix[0].length; j++)
					matrix[i][j] = 0;
			}
		}
		// check from 1 to ensure not to change the first col
		for (int i = 1; i < matrix[0].length; i++) {
			if (matrix[0][i] == 0) {
				for (int j = 1; j < matrix.length; j++)
					matrix[j][i] = 0;
			}
		}
		if (firstRow) {
			for (int i = 0; i < matrix[0].length; i++) {
				matrix[0][i] = 0;
			}
		}
		if (firstCol) {
			for (int i = 0; i < matrix.length; i++) {
				matrix[i][0] = 0;
			}
		}
	}
}

Nice call on the space saving by store the status in first row/column!