Control Statements in Java

Control statements are used to control the flow of execution of a program. Java has three types of control statements:

• Decision-Making Statements
• Looping Statements
• Jump Statements

1. Decision-Making Statements

These statements allow you to control the flow of execution based on certain conditions.

1.1. if Statement

The if statement allows the execution of a block of code only if a specific condition is true.

public class IfStatementExample {
    public static void main(String[] args) {
        int number = 10;
        if (number > 0) {
            System.out.println("Number is positive.");
        }
    }
}
      

Output: Number is positive.

1.2. if-else Statement

The if-else statement executes one block of code if the condition is true, and another block if the condition is false.

public class IfElseStatementExample {
    public static void main(String[] args) {
        int number = -5;
        if (number > 0) {
            System.out.println("Number is positive.");
        } else {
            System.out.println("Number is negative.");
        }
    }
}
      

Output: Number is negative.

1.3. if-else if Statement

The if-else if statement is used to check multiple conditions. It checks each condition sequentially.

public class IfElseIfStatementExample {
    public static void main(String[] args) {
        int number = 0;
        if (number > 0) {
            System.out.println("Number is positive.");
        } else if (number < 0) {
            System.out.println("Number is negative.");
        } else {
            System.out.println("Number is zero.");
        }
    }
}
      

Output: Number is zero.

1.4. switch Statement

The switch statement allows you to test a variable against a series of values (cases). It is an alternative to multiple if-else if statements.

public class SwitchStatementExample {
    public static void main(String[] args) {
        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;
            case 4:
                System.out.println("Thursday");
                break;
            default:
                System.out.println("Invalid day");
        }
    }
}
      

Output: Wednesday

2. Looping Statements

Looping statements are used to repeat a block of code as long as a condition is true.

2.1. for Loop

The for loop is used when you know beforehand how many times you want to execute a statement or a block of statements.

public class ForLoopExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            System.out.println("Iteration number: " + i);
        }
    }
}
      

Output:

Iteration number: 1
Iteration number: 2
Iteration number: 3
Iteration number: 4
Iteration number: 5

2.2. while Loop

The while loop repeats a block of code as long as a given condition is true. The condition is evaluated before the execution of each iteration.

public class WhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        while (i <= 5) {
            System.out.println("Iteration number: " + i);
            i++;
        }
    }
}
      

Output:

Iteration number: 1
Iteration number: 2
Iteration number: 3
Iteration number: 4
Iteration number: 5

2.3. do-while Loop

The do-while loop works similarly to the while loop, but the condition is evaluated after the execution of the loop, meaning the loop is guaranteed to run at least once.

public class DoWhileLoopExample {
    public static void main(String[] args) {
        int i = 1;
        do {
            System.out.println("Iteration number: " + i);
            i++;
        } while (i <= 5);
    }
}
      

Output:

Iteration number: 1
Iteration number: 2
Iteration number: 3
Iteration number: 4
Iteration number: 5

3. Jump Statements

Jump statements are used to transfer control to another part of the program.

3.1. break Statement

The break statement is used to exit from a loop or switch statement prematurely.

public class BreakStatementExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            if (i == 3) {
                break;  // Exits the loop when i is 3
            }
            System.out.println("Iteration number: " + i);
        }
    }
}
      

Output:

Iteration number: 1
Iteration number: 2

3.2. continue Statement

The continue statement is used to skip the current iteration of a loop and continue with the next iteration.

public class ContinueStatementExample {
    public static void main(String[] args) {
        for (int i = 1; i <= 5; i++) {
            if (i == 3) {
                continue;  // Skips the iteration when i is 3
            }
            System.out.println("Iteration number: " + i);
        }
    }
}
      

Output:

Iteration number: 1
Iteration number: 2
Iteration number: 4
Iteration number: 5

3.3. return Statement

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

public class ReturnStatementExample {
    public static void main(String[] args) {
        System.out.println("Sum: " + addNumbers(5, 3));
    }

    public static int addNumbers(int a, int b) {
        return a + b;  // Exits the method and returns the result
    }
}
      

Output: Sum: 8

Summary of Control Statements in Java

Control statements in Java are used to alter the flow of program execution. They are categorized into three main types: Decision-Making Statements, Looping Statements, and Jump Statements. Below is a table summarizing the key control statements with brief descriptions and examples.