printing pattern of stars through arrays in zig zag(snake shape)

I want to print pattern of stars in ZigZag manner....i am unable to break the pattern as zigzag. please help me in doing this public class Pattern3_1 {

public static void main(String[] args) {
    Pattern3_1 pattern = new Pattern3_1();

    pattern.printPattern(5,5);***strong text***
}

public void printPattern(int rows,int coloumns) {
    int index = 0;
    for (int i = 0; i < rows; i++) {

        if (index < rows /2) {
            for (int j = 0; j < coloumns; j++) {
                System.out.print("*");
            }
            System.out.println();

            for (int k = 0; k < i + 1; k++) {
                System.out.print(" ");

            }index++;
        } 
        else {
            for (int j = 0; j < coloumns; j++) {
                System.out.print("*");
            }
            System.out.println();
            for (int k = i + 1; k < rows; k++) {
                System.out.print(" ");
            }
        }
    }
}

} output:

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*****
 *****
*****

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when i try this way i am not getting in ZIGZAG way.... please help me in doing this...........