Question

can someone explain the what the initialize part doing? and how this for loop going to end?

 The for loop generally I see is 
  for(int i =0; i<5; i++){

 }


but the following one is 
 int[][] xx = { {-1,0},  {0,1},{1,0},{0,-1}};


 for(int[] y : xx){
    int i = y[0];
    int j = y[1];


    System.out.println(i+" "+j);
 }

Answer 1

This is called an enhanced for loop. This:

for(int[] y : xx){
    . . .
}

is equivalent to:

for (int index = 0; index < xx.length; ++index) {
    int[] y = xx[index];
    . . .
}

where index is a compiler-generated variable name that does not occur within the body of the for loop.

You can read more about it here and here.