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Why For Loop?

In a while loop, the initialization, condition, and update are written in different places.
This sometimes makes the loop harder to read because the logic is spread out.

The for loop provides a more compact and organized structure by placing all three components in a single line.
This makes it especially useful when the number of iterations is known beforehand.

A for loop is ideal for:

counting loops
iterating fixed ranges
nested iterations
pattern printing
working with arrays and collections

for loop

Syntax

for (initialization; condition; update) {
    // statements
}

Meaning of Each Part

initialization → runs once before the loop starts
condition → checked before every iteration
update → runs after each loop iteration

If the condition becomes false, the loop stops.

Example 1 – Simple For Loop

for (int i = 1; i <= 4; i++) {
    System.out.println("Hi " + i);
}

Output

Hi 1
Hi 2
Hi 3
Hi 4

Explanation

Loop starts with i = 1
Runs as long as i <= 4
Prints each value of i
i++ increases the counter after every iteration

This is the most common use of a for loop—simple counting.

Example 2 – Nested For Loop

for (int i = 1; i <= 4; i++) {
    System.out.println("Day " + i);

    for (int j = 1; j < 9; j++) {
        System.out.println(" " + (j + 8));
    }
}

Sample Output

Explanation

The outer loop runs 4 times — representing days.
For each day, the inner loop prints numbers from 9 to 16.
This structure is extremely common when dealing with rows and columns, grids, tables, or patterns.

Nested loops allow repetitive tasks inside repetitive tasks.

Special Usage of the For Loop

1. Infinite Loop

for (;;) {
    System.out.println("Running forever...");
}

Explanation

All parts are empty.
Condition defaults to true, so the loop never ends.
Same as:

while (true) { }

Infinite loops are often used in game loops, server listeners, etc.

2. For Loop as a While Loop

You can leave the initialization or update part empty:

int i = 1;
for (; i <= 4;) {
    System.out.println("Hi " + i);
    i++;
}

Explanation

Initialization is done outside the loop.
Update is done manually inside the loop.
Behavior becomes identical to:

while (i <= 4) { }

This shows how flexible a for loop can be.

3. Multiple Updates in One For Statement

for (int i = 1, j = 5; i <= j; i++, j--) {
    System.out.println(i + " " + j);
}

Explanation

You can initialize multiple variables.
And update multiple variables in each iteration.
This is useful in algorithms where two indices move towards each other, such as:
- checking palindrome strings
- working with two-pointer techniques
- merging data

Key Notes

for loop is best when the number of iterations is known in advance.
It keeps initialization, condition, and update neatly together—making code more readable.
The loop is flexible:
- Can become an infinite loop
- Can mimic a while loop
- Can use multiple counters
Common tool for patterns, counting tasks, arrays, and nested structures.

Written By: Shiva Srivastava

For Loop

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