Loops

Loops in Java are used to execute a block of code repeatedly. They allow you to iterate over a sequence of elements or execute a block of code until a certain condition is met. In this tutorial, we will learn about loops in Java.

for Loop

The for loop is used to iterate over a sequence of elements a fixed number of times. It consists of three parts: initialization, condition, and increment/decrement. The basic syntax of the for loop is as follows:

for (initialization; condition; increment/decrement) {
    // code block to be executed
}

Here is an example of using the for loop to print numbers from 1 to 5:

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

In the above example, the for loop iterates over the numbers from 1 to 5 and prints each number to the console.

while Loop

The while loop is used to execute a block of code repeatedly as long as a specified condition is true. The loop continues to execute until the condition becomes false. The basic syntax of the while loop is as follows:

while (condition) {
    // code block to be executed
}

Here is an example of using the while loop to print numbers from 1 to 5:

int i = 1;

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

In the above example, the while loop iterates over the numbers from 1 to 5 and prints each number to the console.

do-while Loop

The do-while loop is similar to the while loop, but the condition is checked after the block of code is executed. This means that the block of code is executed at least once, even if the condition is false. The basic syntax of the do-while loop is as follows:

do {
    // code block to be executed
} while (condition);

Here is an example of using the do-while loop to print numbers from 1 to 5:

int i = 1;

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

In the above example, the do-while loop iterates over the numbers from 1 to 5 and prints each number to the console.

Loop Control Statements

Java provides loop control statements that allow you to control the flow of the loop. The loop control statements include break, continue, and return.

break Statement

The break statement is used to exit the loop prematurely. It is often used to terminate the loop when a certain condition is met. When the break statement is encountered, the loop is terminated, and the control is transferred to the statement following the loop.

Here is an example of using the break statement to exit a loop when the value of i is 3:

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

In the above example, the loop is terminated when the value of i is 3.

continue Statement

The continue statement is used to skip the current iteration of the loop and continue with the next iteration. It is often used to skip certain elements in the loop based on a condition.

Here is an example of using the continue statement to skip printing even numbers:

for (int i = 1; i <= 5; i++) {
    if (i % 2 == 0) {
        continue;
    }
    System.out.println(i);
}

In the above example, the loop skips printing even numbers using the continue statement.

return Statement

The return statement is used to exit a method prematurely. When the return statement is encountered inside a loop, the loop is terminated, and the control is transferred back to the caller of the method.

Here is an example of using the return statement inside a loop:

public void printNumbers() {
    for (int i = 1; i <= 5; i++) {
        if (i == 3) {
            return;
        }
        System.out.println(i);
    }
}

In the above example, the loop is terminated when the value of i is 3 using the return statement.

Nested Loops

Nested loops are loops inside another loop. They are used to perform repetitive tasks that require multiple levels of iteration. Nested loops can be of any type, such as for, while, or do-while.

Here is an example of using nested loops to print a pattern:

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

In the above example, the nested loops are used to print a pattern of stars.