Let’s go deep into the for loop in Java — one of the most common and powerful looping structures.
🔁 What is a for Loop?
A for loop allows you to execute a block of code a known number of times. It's perfect when you know in advance how many times you want to run the loop.
🧠 Syntax:
for (initialization; condition; update) {
// Code to execute in each loop iteration
}
🔍 Parts of a for Loop:
| Part | Description |
|---|---|
| Initialization | Runs once at the start. Sets up the loop counter. |
| Condition | Checked before each iteration. Loop runs as long as it's true. |
| Update | Runs after each iteration. Usually used to increment/decrement counter. |
✅ Basic Example:
public class ForLoopExample {
public static void main(String[] args) {
for (int i = 1; i <= 5; i++) {
System.out.println("i = " + i);
}
}
}🔎 Output:
i = 1
i = 2
i = 3
i = 4
i = 5🔁 Reverse Loop Example:
for (int i = 5; i >= 1; i--) {
System.out.println(i);
}Output:
5
4
3
2
1💥 Infinite Loop (Be careful!)
for (;;) {
System.out.println("This runs forever!");
}If you leave all 3 parts empty, it becomes an infinite loop. Use with caution!
🔍 Nested for Loops:
Used for patterns or matrices:
for (int i = 1; i <= 3; i++) {
for (int j = 1; j <= 2; j++) {
System.out.println("i=" + i + ", j=" + j);
}
}
🆚 Compared with while and do-while:
| Feature |
for loop |
while loop |
do-while loop |
|---|---|---|---|
| Condition check | Before each iteration | Before each iteration | After each iteration |
| Usage | When count is known | When count is unknown | Must run at least once |
🎯 Common Use Cases:
- Iterating through arrays
- Printing patterns
- Counting logic
- Repeated tasks with a known range