为什么以下代码显示“ 0 1 2 3”？

Question

in this code im confused as to why it prints out "0 1 2 3" instead of "3 2 1 0"

    int y = 3;
    String s = " ";
    while (y>-1)
    {
        s = y + " " + s;
        y--;
    }
    System.out.print(s);

Thanks.

Answer 1

s = y + " " + s;

adds y at the front of the string so:

s = 3 
s = 2 3
s = 1 2 3
s = 0 1 2 3

Answer 2

step 1:
s = 3

step 2:
s = 2 3;

step 3:
s = 1 2 3

like wise in every loop y's value is added to the starting point of the string s

Answer 3

This is because you prepend the newest value to the string. If you want the output to be "3 2 1 0" you should change your line from

s = y + " " + s;

to

s = s + " " + y;