Java Iteration Statements – Complete Beginner Guide

Iteration statements allow Java programs to repeat tasks automatically. Loops are essential for performing repetitive tasks efficiently.

1. Introduction to Iteration

Iteration means executing a block of code repeatedly. Java provides multiple loop structures, each useful for different scenarios.

Main loops: while, do-while, for, nested for, for-each.

The while loop checks the condition first and executes the block only while the condition is true.

int i = 1;
while(i <= 5){
    System.out.println(i);
    i++;
}

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The do-while loop executes at least once, because the condition is checked after running the loop body.

int x = 1;
do{
    System.out.println(x);
    x++;
}while(x <= 3);

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The for loop is used when the number of iterations is known in advance.

for(int k = 1; k <= 5; k++){
    System.out.println(k);
}

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Using a loop inside another loop allows multi-level repetition. Useful in matrix operations and pattern printing.

for(int i = 1; i <= 3; i++){
    for(int j = 1; j <= 3; j++){
        System.out.println(i + \" \" + j);
    }
}

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1 2
1 3
2 1
2 2
2 3
3 1
3 2
3 3

The for-each loop is used for easy traversal of arrays and collections.

int nums[] = {10, 20, 30};
for(int n : nums){
    System.out.println(n);
}

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30

break immediately stops the loop execution.

for(int i = 1; i <= 5; i++){
    if(i == 3) break;
    System.out.println(i);
}

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continue skips the current loop iteration and proceeds with the next.

for(int i = 1; i <= 5; i++){
    if(i == 3) continue;
    System.out.println(i);
}

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1️⃣ Difference between while and do–while?

while checks before; do–while checks after, so it executes at least once.

2️⃣ Best loop for fixed number of iterations?

The for loop.

3️⃣ What does break do?

Stops the loop immediately.

4️⃣ What does continue do?

Skips the current iteration.

5️⃣ What is a nested loop?

A loop inside another loop.