Java For Loop
When you know exactly how many times you want to loop through a block of code, use the for loop instead of a while loop:
Syntax
for (statement 1; statement 2; statement 3) {
// code block to be executed
}
Statement 1 is executed (one time) before the execution of the code block.
Statement 2 defines the condition for executing the code block.
Statement 3 is executed (every time) after the code block has been executed.
Print Numbers
The example below will print the numbers 0 to 4:
Example
for (int i = 0; i < 5; i++) {
System.out.println(i);
}
Example explained
- Statement 1 sets a variable before the loop starts:
int i = 0 - Statement 2 defines the condition for the loop to run:
i < 5. If the condition is true, the loop will run again; if it is false, the loop ends. - Statement 3 increases a value each time the code block has run:
i++
Print Even Numbers
This example prints even values between 0 and 10:
Example
for (int i = 0; i <= 10; i = i + 2) {
System.out.println(i);
}
Sum of Numbers
This example calculates the sum of numbers from 1 to 5:
Example
int sum = 0;
for (int i = 1; i <= 5; i++) {
sum = sum + i;
}
System.out.println("Sum is " + sum);
Countdown
This example prints a countdown from 5 to 1:
Example
for (int i = 5; i > 0; i--) {
System.out.println(i);
}
For Loop With False Condition
Just like a while loop, a for loop may also never run. If the condition is false right from the start, the code inside the loop will be skipped entirely:
Example
for (int i = 10; i < 5; i++) {
System.out.println("This will never be printed");
}
In this example, the loop starts with i = 10. The condition i < 5 is already false, so the loop body is skipped, and nothing is printed.
