Control statements in Java are essential for controlling the flow of execution in a program. They allow you to make decisions, execute certain blocks of code conditionally, or repeat blocks of code based on specific conditions. Java has three main categories of control statements:

1. Conditional Statements
2. Looping Statements
3. Jump Statements

Let's explore each of these categories in detail.

1. Conditional Statements

Conditional statements allow you to execute a block of code based on whether a specified condition evaluates to true or false.

a. if Statement

The if statement executes a block of code if its condition is true.

Example:

int number = 10;
if (number > 0) {
    System.out.println("The number is positive.");
}

b. if-else Statement

The if-else statement provides an alternative block of code to execute when the condition is false.

Example:

int number = -5;
if (number > 0) {
    System.out.println("The number is positive.");
} else {
    System.out.println("The number is not positive.");
}

c. if-else if-else Statement

This structure allows you to check multiple conditions.

Example:

int number = 0;
if (number > 0) {
    System.out.println("The number is positive.");
} else if (number < 0) {
    System.out.println("The number is negative.");
} else {
    System.out.println("The number is zero.");
}

d. switch Statement

The switch statement allows you to execute one block of code among many based on the value of a variable.

Example:

int day = 3;
switch (day) {
    case 1:
        System.out.println("Monday");
        break;
    case 2:
        System.out.println("Tuesday");
        break;
    case 3:
        System.out.println("Wednesday");
        break;
    default:
        System.out.println("Invalid day");
}

2. Looping Statements

Looping statements allow you to execute a block of code repeatedly based on a condition.

a. for Loop

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

Example:

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

b. while Loop

The while loop continues executing as long as the specified condition is true. It is used when the number of iterations is not known in advance.

Example:

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

c. do-while Loop

The do-while loop is similar to the while loop, but it guarantees that the block of code will execute at least once.

Example:

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

3. Jump Statements

Jump statements allow you to alter the flow of control in your program.

a. break Statement

The break statement is used to terminate a loop or a switch statement immediately.

Example:

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        break; // Exit the loop when i is 3
    }
    System.out.println("Iteration: " + i);
}
// Output: Iteration: 1
//         Iteration: 2

b. continue Statement

The continue statement skips the current iteration of a loop and moves to the next iteration.

Example:

for (int i = 1; i <= 5; i++) {
    if (i == 3) {
        continue; // Skip the iteration when i is 3
    }
    System.out.println("Iteration: " + i);
}
// Output: Iteration: 1
//         Iteration: 2
//         Iteration: 4
//         Iteration: 5

c. return Statement

The return statement is used to exit a method and optionally return a value.

Example:

public class ReturnExample {
    public static int add(int a, int b) {
        return a + b; // Exit the method and return the sum
    }

    public static void main(String[] args) {
        int sum = add(5, 10);
        System.out.println("Sum: " + sum); // Output: Sum: 15
    }
}

Summary

Control statements in Java play a crucial role in defining the flow of execution in a program. Understanding how to use conditional statements, looping statements, and jump statements effectively allows you to write more flexible and powerful Java applications. Mastery of these control statements is essential for any Java programmer.