Java If-Else Conditions: If, Else-If Ladder and Nested Decisions

Conditional statements enable programs to make intelligent decisions at runtime based on dynamically changing input data. In Java, decision making is primarily governed by the if, if-else, if-else-if ladder, and nested if constructs.

Figure 4: Decision Tree and Execution Flow of Java Branching and Loop Constructs.

1. Simple If Statement

Executes a block of code strictly when the specified condition evaluates to true:

int accountBalance = 1500;
if (accountBalance > 1000) {
    System.out.println("Sufficient funds for transaction!");
}

2. The If-Else Statement

Provides a fallback alternative when the condition evaluates to false:

int age = 17;
if (age >= 18) {
    System.out.println("Eligible to Vote!");
} else {
    System.out.println("Underage: Not eligible to vote yet.");
}

3. The If-Else-If Ladder

Evaluates multiple mutually exclusive conditions in sequential top-down order. The moment a condition tests true, its block runs and the remaining branches are bypassed:

public class GradeCalculator {
    public static void main(String[] args) {
        int score = 85;

        if (score >= 90) {
            System.out.println("Grade: A+ (Outstanding)");
        } else if (score >= 80) {
            System.out.println("Grade: A (Distinction)");
        } else if (score >= 70) {
            System.out.println("Grade: B (First Class)");
        } else if (score >= 50) {
            System.out.println("Grade: C (Second Class)");
        } else if (score >= 40) {
            System.out.println("Grade: D (Pass)");
        } else {
            System.out.println("Grade: F (Fail)");
        }
    }
}

4. Nested If Statements & Best Practices

A nested if is an if statement placed inside the body of an outer if or else block. It is useful when secondary checks depend strictly on the success of a primary validation:

boolean isAccountActive = true;
double withdrawalAmount = 5000.0;
double currentBalance = 12000.0;

if (isAccountActive) {
    // Nested secondary check
    if (withdrawalAmount <= currentBalance) {
        currentBalance -= withdrawalAmount;
        System.out.println("Withdrawal Successful! Remaining: $" + currentBalance);
    } else {
        System.out.println("Transaction Failed: Insufficient funds.");
    }
} else {
    System.out.println("Transaction Failed: Account is frozen or inactive.");
}

boolean flag = false;
if (flag = true) {
    System.out.println("TRUE");
} else {
    System.out.println("FALSE");
}