array assignment within the FOR statement

[Alex Ku]

hi,

  
  public static void main(String args[])
  {
    int [] nArray = new int[11];
    int i;
    for (i = 0; i < 10; nArray[i++] = i)
    {
      System.out.println(i + ":" + nArray[i]);
    }
  }

The code above has following output:
0:0
1:0
2:0
3:0
4:0
5:0
6:0
7:0
8:0
9:0
However, if the code is changed to this:
(print out the result in another for-loop

  
  public static void main(String args[])
  {
    int [] nArray = new int[11];
    int i;
    for (i = 0; i < 10; nArray[i++] = i);
    for (i = 0; i < 10; i++)
    {
      System.out.println(i + ":" + nArray[i]);
    }
  }

The output is:
0:1
1:2
2:3
3:4
4:5
5:6
6:7
7:8
8:9
9:10
Why???
Thanks
kawaii

[Shivaji Marathe]

The last part of the for loop ( the one after the second semicolon ) is executed after each iteration of the loop, not before.
In the first example the assignment to i and the comparison happen before the println statements and the assignment to the array happen after each iteration.
In the second example the print statements are executed in a separate for loop, that executes after the first one is complete and therefore all the assignments to the array are complete.
HTH

[Dave Vick]

Kawaii
In your first example keep in mind that the increment part of the for loop is executed at the end of the loop.

  
  public static void main(String args[])
  {
    int [] nArray = new int[11];
    int i;
    for (i = 0; i < 10; nArray[i++] = i)
    {
      System.out.println(i + ":" + nArray[i]);
    }
  }

When the first println is reached i is still 0, then at the end of the for loop, right after the println, the value of nArray[0] is set to 1 then it loops again. Now i is 1 and the value of nArray[1] is still 0 (the default), and so on. You are always printing the value of the element you ahven't reached yet.
In your second example you first loop through and assign all of the array elements a value then you print out the values.

  
  public static void main(String args[])
  {
    int [] nArray = new int[11];
    int i;
    for (i = 0; i < 10; nArray[i++] = i);
    for (i = 0; i < 10; i++)
    {
      System.out.println(i + ":" + nArray[i]);
    }
  }

hope that helps
[ March 11, 2002: Message edited by: Dave Vick ]