Control Flow Statements

Control statements in Java allow a program to make decisions, repeat tasks, and control the flow of execution based on conditions. Without control statements, a Java program would execute line by line with no flexibility. By using conditional statements and loops, developers can build intelligent, dynamic, and efficient programs.

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1. if Statement

Description

The if statement is used to execute a block of code only when a specific condition is true. If the condition evaluates to false, the code inside the if block is skipped.

Syntax

if (condition) {
    // code to execute
}

Example

int age = 20;

if (age >= 18) {
    System.out.println("You are eligible to vote.");
}

Explanation

If the value of age is 18 or above, the message is printed. Otherwise, nothing happens.

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2. if-else Statement

Description

The if-else statement provides two execution paths. One block runs if the condition is true, and the other runs if the condition is false.

Syntax

if (condition) {
    // true block
} else {
    // false block
}

Example

int marks = 45;

if (marks >= 50) {
    System.out.println("Pass");
} else {
    System.out.println("Fail");
}

Explanation

If marks are 50 or above, the student passes; otherwise, the student fails.

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3. Nested if Statement

Description

A nested if statement is an if statement inside another if. It is used when multiple conditions must be checked in a specific order.

Syntax

if (condition1) {
    if (condition2) {
        // code
    }
}

Example

int age = 22;
boolean hasID = true;

if (age >= 18) {
    if (hasID) {
        System.out.println("Entry allowed.");
    }
}

Explanation

The message is printed only if both conditions are satisfied.

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4. switch-case Statement

Description

The switch-case statement is used to execute one block of code from multiple choices based on the value of a variable. It is often used as an alternative to long if-else-if chains.

Syntax

switch (expression) {
    case value1:
        // code
        break;
    case value2:
        // code
        break;
    default:
        // code
}

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");
}

Explanation

The program prints the day corresponding to the given number. The break statement prevents fall-through.

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5. Ternary Operator

Description

The ternary operator is a short-hand alternative to if-else. It evaluates a condition and returns one of two values.

Syntax

condition ? value_if_true : value_if_false;

Example

int number = 10;

String result = (number % 2 == 0) ? "Even" : "Odd";
System.out.println(result);

Explanation

If the number is divisible by 2, it prints “Even”; otherwise, it prints “Odd”.

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6. for Loop

Description

The for loop is used when the number of iterations is known in advance. It consists of initialization, condition, and increment/decrement.

Syntax

for (initialization; condition; increment/decrement) {
    // code
}

Example

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

Explanation

The loop prints numbers from 1 to 5.

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7. while Loop

Description

The while loop executes a block of code as long as the condition is true. The condition is checked before each iteration.

Syntax

while (condition) {
    // code
}

Example

int i = 1;

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

Explanation

The loop prints numbers from 1 to 5.

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8. do-while Loop

Description

The do-while loop executes the code at least once, even if the condition is false, because the condition is checked after execution.

Syntax

do {
    // code
} while (condition);

Example

int i = 1;

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

Explanation

The loop prints numbers from 1 to 5, guaranteeing at least one execution.

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9. break Statement

Description

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

Example

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

Explanation

The loop stops when i becomes 3.

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10. continue Statement

Description

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

Example

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

Explanation

The number 3 is skipped, and the loop continues with the next value.