Conditional Statements

Summary of Conditional Statements

1. if Statement

The if statement is used to execute a block of code only if a specified condition is true.

Syntax

if (condition) {
    // Code to execute if condition is true
}

Example

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

2. if-else Statement

The if-else statement is used to execute one block of code if the condition is true and another block if the condition is false.

Syntax

if (condition) {
    // Code to execute if condition is true
} else {
    // Code to execute if condition is false
}

Example

int number = -5;
if (number > 0) {
    System.out.println("The number is positive.");
} else {
    System.out.println("The number is negative.");
}

3. if-else-if Ladder

The if-else-if ladder is used when there are multiple conditions to check.

Syntax

if (condition1) {
    // Code to execute if condition1 is true
} else if (condition2) {
    // Code to execute if condition2 is true
} else {
    // Code to execute if none of the conditions are true
}

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.");
}

4. Nested if Statements

An if statement can be used inside another if statement to perform additional checks.

Syntax

if (condition1) {
    if (condition2) {
        // Code to execute if both conditions are true
    }
}

Example

int number = 5;
if (number > 0) {
    if (number % 2 == 0) {
        System.out.println("The number is positive and even.");
    } else {
        System.out.println("The number is positive and odd.");
    }
}

5. switch Statement

The switch statement is used to execute one block of code from many options based on the value of a variable or expression.

Syntax

switch (expression) {
    case value1:
        // Code to execute if expression == value1
        break;
    case value2:
        // Code to execute if expression == value2
        break;
    ...
    default:
        // Code to execute if no case matches
}

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");
}

Key Points

• Use the break statement to terminate a case. Without break, the program executes all subsequent cases (fall-through).
• The default block is optional but executes if no case matches.

Comparison of if-else and switch

6. Conditional (Ternary) Operator

The conditional operator (? :) is a shorthand for if-else.

Syntax

condition ? expression1 : expression2;

Example

int number = 5;
String result = (number > 0) ? "Positive" : "Negative";
System.out.println(result); // Output: Positive