TwoDimArray.java

// class twoDimArray
// ...practice working with 2D arrays

public class TwoDimArray 
{

    //postcond: prints each row of 2D integer array a on its own line
    //          uses a FOR loop
    public static void print1( int[][] a ) { 
	for( int i = 0; i < a.length; i++ ) {
	    for( int j = 0; j < a[i].length; j++ ) 
		System.out.print( a[i][j] + " " );
	    System.out.println();
	}
    }


    //postcond: prints each row of 2D integer array a on its own line
    //          uses a FOREACH loop
    public static void print2( int[][] a ) { 
	for( int [] row : a ) {
	    for( int col : row) 
		System.out.print(col +  " " );
	    System.out.println();
	}
    }


    //postcond: returns sum of all items in 2D integer array a
    public static int sum1( int[][] a ) { 
	int sum = 0;
	for( int [] row : a ) {
	    for( int col : row) 
		sum += col;
	}
	return sum;
    }


    //postcond: returns sum of all items in 2D integer array a
    //          * uses helper fxn sumRow
    public static int sum2( int [][] m ) { 
	int sum = 0;
	for( int r = 0; r < m.length; r++ ) {
	    sum = sumRow( r, m );
	}
	return sum;
    }


    //postcond: returns sum of all items on row r of 2D integer array a
    //          uses a FOR loop
    public static int sumRow( int r, int[][] a ) { 
	int ans = 0;
	for( int i = 0; i  < a[r].length; i++ ) {
	    ans += a[r][i];
	}
	return ans;
    }


    //postcond: returns sum of all items on row r of 2D integer array a
    //          uses a FOREACH loop
    public static int sumRow2( int r, int[][] m ) { 
	int sum = 0;
	for( int num : m[r] ) {
	    sum += num;
	}
	return sum;
    }


    public static void main( String [] args ) {

	int [][] m1 = new int[4][2];
	int [][] m2 = { {2,4,6}, {3,5,7} };
	int [][] m3 = { {2}, {4,6}, {1,3,5} };
	print1(m1);
	print1(m2);
	print1(m3);
	print2(m1);
	print2(m2);
	print2(m3);
	System.out.print("testing sum1...\n");
	System.out.println("sum m1 : " + sum1(m1));
	System.out.println("sum m2 : " + sum1(m2));
	System.out.println("sum m3 : " + sum1(m3));
	System.out.print("testing sum2...\n");
	System.out.println("sum m1 : " + sum2(m1));
	System.out.println("sum m2 : " + sum2(m2));
	System.out.println("sum m3 : " + sum2(m3));

    }

}//end class TwoDimArray