ZigZag printer

zigzag.java

public class ZigZag{

     public static void main(String []args){
        String str = "thisisazigzag";
         
        System.out.println(str);
        printZigZag(str, 4);
     }
     
     public static void printZigZag(String input, int levels) {
        
        char[][] charMatrix = new char[levels][input.length()];
        
        for(int i = 0; i < levels; i++) {
            for(int j = 0; j < input.length(); j++) {
                charMatrix[i][j] = ' ';
            }
        }
        
        int rowNum = 0;
        int colNum = 0;
        int increment = 1;
        for(int i = 0; i < input.length(); i++) {
            colNum = i;
            
            charMatrix[rowNum][colNum] = input.charAt(i);
            
            rowNum += increment; 
             
            if (rowNum >= levels) {
                rowNum = levels - 2;
                increment = -1;
            } else if (rowNum < 0) {
                rowNum = 1;
                increment = 1;
            }
        }
        
        for(int i = 0; i < levels; i++) {
            for(int j = 0; j < input.length(); j++) {
                System.out.print(charMatrix[i][j]);
            }
            System.out.println();
        }
     }
}