terminates. The iteration expression determines how the loop control variable is changed
each time the loop iterates. Here is a short program that illustrates the for loop:
/*
Demonstrate the for loop.
Call this file "ForTest.java".
*/
class ForTest {
public static void main(String args[]) {
int x;
for(x = 0; x<10; x = x+1)
System.out.println("This is x: " + x);
}
}
This program generates the following output:
This
is
x:
0
This
is
x:
1
This
is
x:
2
This
is
x:
3
This
is
x:
4
This
is
x:
5
This
is
x:
6
This
is
x:
7
This
is
x:
8
This
is
x:
9
In this example, x is the loop control variable. It is initialized to zero in the initialization portion
of the for. At the start of each iteration (including the first one), the conditional test x < 10 is
performed. If the outcome of this test is true, the println( ) statement is executed, and then
the iteration portion of the loop is executed. This process continues until the conditional test
is false.
As a point of interest, in professionally written Java programs you will almost never see
the iteration portion of the loop written as shown in the preceding program. That is, you will
seldom see statements like this:
x = x + 1;
The reason is that Java includes a special increment operator which performs this operation
more efficiently. The increment operator is ++. (That is, two plus signs back to back.) The
increment operator increases its operand by one. By use of the increment operator, the
preceding statement can be written like this:
x++;
Thus, the for in the preceding program will usually be written like this:
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