Why this problem print 0 0 3 0 1?

Question

int[] a = {1, 2, 3, 4, 1};

for(int n:a)
a[n]=0;

for(int n:a)
System.out.println(n);

Answer 1

It loops through the array values, not indexes.
First step:
n=1;
a[1]=0;
[1, 0, 3, 0 1]
Second step:
n=0;
a[0]=0;
[0, 0, 3, 0, 1]
And so on