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Control Flow

Thinking

Control flow structures form the backbone of decision-making in programming. They allow code to execute conditionally or repeatedly, adapting to various input and logic scenarios.

In Java, mastering `if`, `if-else`, and `switch` statements helps you write dynamic programs that respond intelligently to different data and user inputs.

Description

Java provides several control flow mechanisms to determine the direction in which a program proceeds based on certain conditions. The primary conditional constructs include:

  • if statement: Executes a block of code only if a specified condition is true.
  • if-else statement: Executes one block if the condition is true, another if it's false.
  • if-else-if ladder: Tests multiple conditions sequentially.
  • switch statement: Selects one of many code blocks to execute based on the value of a variable.

Using these effectively allows developers to build intelligent logic flows, making applications responsive and flexible.

Video Resources

Switch Statements

Mastering the switch-case logic in Java with examples.

View PDF

Examples (code)

Using if-else


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

        if(score >= 90) {
            System.out.println("Grade A");
        } else if(score >= 75) {
            System.out.println("Grade B");
        } else {
            System.out.println("Grade C");
        }
    }
}

Using switch-case


public class SwitchExample {
    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;
            default:
                System.out.println("Another Day");
        }
    }
}

Real-World Applications

Authentication Systems

Decide access levels and user permissions using control flow logic.

Traffic Signal Controllers

Switch statements help control light transitions based on timers or sensor input.

Game Development

Use nested if-else conditions for player actions, scoring, and game states.

Interview Questions

Q1: What is the difference between if-else and switch?

Show Answer

If-else allows complex conditional expressions, whereas switch is more readable and efficient for equality checks on a single variable.

Q2: Can we use strings in switch statements?

Show Answer

Yes, from Java 7 onwards, switch statements support String as the control expression.

Q3: What happens if we forget the break in a switch case?

Show Answer

If the break statement is omitted, Java will execute all subsequent cases until it encounters a break or the switch ends (known as fall-through).