Java Decision Marking and Branching

 Java decision-making

 

Java decision-making refers to how Java programs make choices or determine the flow of execution based on conditions. The most common structures for decision-making in Java include:

1. if Statement

2. if-else Statement

3. else if` Ladder

4. switch Statement

1. if Statement

The `if` statement evaluates a condition and executes a block of code if the condition is `true`.

Syntax:
if (condition) {
    // code to be executed if condition is true
}

Example:

int age = 18;
if (age >= 18) {
    System.out.println("You are an adult.");
}
 

 2. if-else Statement

The `if-else` statement allows for two outcomes: one if the condition is `true`, and another if it is `false`.

if (condition) {
    // code to be executed if condition is true
} else {
    // code to be executed if condition is false
}

Example:

int age = 16;
if (age >= 18) {
    System.out.println("You are an adult.");
} else {
    System.out.println("You are a minor.");
}

3. else if` Ladder

The `else if` statement is used when there are multiple conditions to evaluate.

if (condition1) {
    // code to be executed if condition1 is true
} else if (condition2) {
    // code to be executed if condition2 is true
} else {
    // code to be executed if all conditions are false
}

Example:

int score = 85;
if (score >= 90) {
    System.out.println("Grade: A");
} else if (score >= 80) {
    System.out.println("Grade: B");
} else {
    System.out.println("Grade: C");
}

 

4.Nested `if` statement

In Java, a nested `if` statement is when you place one `if` statement inside another `if` (or `else if` or `else`) statement. This allows for testing multiple conditions in a hierarchical way, meaning the inner `if` is only evaluated if the outer `if` condition is true.

Syntax:

if (condition1) {

    // Executes when condition1 is true

    if (condition2) {

        // Executes when both condition1 and condition2 are true

    } else {

        // Executes when condition1 is true but condition2 is false

    }

} else {

    // Executes when condition1 is false

}

Example: Age and Gender Classification

Let's say we want to check a person’s age and gender to classify them into different categories.

 

class Main {

    public static void main(String[] args) {

        int age = 25;

        String gender = "Male";

       

        // Outer if statement to check age

        if (age >= 18) {

            System.out.println("Adult");

           

            // Nested if to check gender

            if (gender.equals("Male")) {

                System.out.println("Adult Male");

            } else {

                System.out.println("Adult Female");

            }

        } else {

            System.out.println("Minor");

        }

    }

}

5. switch Statement

The `switch` statement is an alternative to the `if-else` structure, often used when comparing a variable to multiple possible values.

switch (variable) {
    case value1:
        // code to be executed if variable == value1
        break;
    case value2:
        // code to be executed if variable == value2
        break;
    default:
        // code to be executed if variable doesn't match any case
}


Example:

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

5. Ternary Operator ( ? : )The ternary operator is a shorthand for `if-else` statements.

variable = (condition) ? expression1 : expression2;


Example:

int age = 20;
String status = (age >= 18) ? "Adult" : "Minor";
System.out.println(status);

These structures help control the program flow, allowing Java applications to react to different inputs or conditions efficiently. 

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