for Loop — Java

Java for Loop

What is a for Loop?

A for loop repeats a block of code a known number of times. It packs the three things every counting loop needs — where to start, when to stop, and how to move forward — into a single, tidy header line.

Basic Syntax

Java

for (initialization; condition; update) {
    // code to repeat
}

initialization runs once, before the loop starts (usually declares a counter).
condition is checked before every iteration — the loop keeps running while it's true.
update runs after every iteration (usually increments or decrements the counter).

A Simple Example

Java

for (int i = 1; i <= 5; i++) {
    System.out.println("Count: " + i);
}

Count: 1
Count: 2
Count: 3
Count: 4
Count: 5

Note

i is scoped to the loop — it only exists inside the for loop's braces and disappears once the loop finishes.

Counting Down

Java

for (int i = 5; i >= 1; i--) {
    System.out.println(i);
}
System.out.println("Liftoff!");

5
4
3
2
1
Liftoff!

Multiple Init and Update Expressions

The header isn't limited to a single variable. You can initialize and update more than one variable at once by separating them with commas — handy when two counters need to move together.

Java

for (int i = 0, j = 10; i < j; i++, j--) {
    System.out.println("i = " + i + ", j = " + j);
}

i = 0, j = 10
i = 1, j = 9
i = 2, j = 8
i = 3, j = 7
i = 4, j = 6

Nested for Loops

A for loop can contain another for loop. This is the standard tool for working with grids, tables, and anything two-dimensional — the outer loop picks a row, the inner loop walks across the columns of that row.

Java

for (int row = 1; row <= 3; row++) {
    for (int col = 1; col <= 3; col++) {
        System.out.print(row + "," + col + "  ");
    }
    System.out.println();
}

1,1  1,2  1,3
2,1  2,2  2,3
3,1  3,2  3,3

Tip

The inner loop completes ALL of its iterations for every single iteration of the outer loop. For a 3x3 grid, the inner println runs 9 times total (3 outer x 3 inner).

Classic for vs Enhanced for

Java also has an enhanced for loop (the "for-each" loop) that reads more naturally when you just want to visit every element of an array or collection without caring about the index. It's covered in detail on the next page — but as a quick preview:

Situation	Better Choice
You need the index (e.g., i, or comparing i to another counter)	Classic for
You're counting up/down, skipping values, or using multiple counters	Classic for
You just want every element of an array/collection, in order	Enhanced for
You want to modify elements by index (arr[i] = ...)	Classic for

Practice Exercises

Print all even numbers between 1 and 20 using a for loop.
Print a multiplication table for a given number using a for loop.
Use a nested for loop to print a triangle pattern of asterisks.
Use two counters in one for loop header to print pairs that add up to 10.