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If-Else Statements

Caleb Thomas

Caleb Thomas

5 min read

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Study Guide Overview

This study guide covers if-else statements in Java, including syntax, code blocks, and practical examples like a rounding method. It also provides practice questions with solutions and a scoring guide. Finally, it highlights key exam topics like Object-Oriented Programming, Arrays and ArrayLists, Recursion, and Sorting and Searching, along with common question types and last-minute exam tips.

AP Computer Science A: Ultimate Study Guide

Hey there! Let's get you prepped and confident for your AP Computer Science A exam. This guide is designed to be your go-to resource, especially the night before the test. We'll keep it clear, engaging, and super focused on what you need to know. Let's dive in!

Control Structures

If-Else Statements

So, we've tackled if statements, but what happens when the condition is false? That's where the else statement jumps in! Think of it as the backup plan. If the if condition isn't met, the else block executes. Together, they form an if-else statement, a two-way street for your code.

// some code that runs before conditional statement
if (condition) { 
  // code that runs if the condition is true
} else {
  // code that runs if the condition is false
}
// some code that runs after
Key Concept

Remember those curly braces {}? They're super important! They define the code blocks for both if and else. Always use them to avoid confusion and keep your code organized. Indentation also helps a lot to keep the code readable!

Example: Number Rounding

Let's put this into action with a rounding method. No more manual rounding! 🚀

public static int round(double number) {
  if (number >= 0) {
    return (int) (number + 0.5);
  } else {
    return (int) (number - 0.5);
  }
}
Memory Aid

Think of if-else as a fork in the road. If the condition is true, you go one way (the if block); otherwise, you take the other path (the else block).

Common Mistake

Forgetting the curly braces {}! This can lead to unexpected behavior and logic errors. Always use them to define your code blocks.

Practice Questions

Practice Question

Multiple Choice Questions

  1. What is the output of the following code snippet?
int x = 5;
if (x > 10) {
  System.out.print("A");
} else {
  System.out.print("B");
}

a) A
b) B
c) A B
d) No output

2. Which of the following is the correct syntax for an if-else statement? a) if condition { } else { } b) if (condition) { } else { } c) if condition then { } else { } d) if (condition) then { } else { }

Free Response Question

Write a method called checkEvenOdd that takes an integer as a parameter and prints "Even" if the number is even and "Odd" if the number is odd. You must use an if-else statement.

public static void checkEvenOdd(int num) {
  // your code here
}

Scoring Guide

  • +1 point for correct method signature
  • +1 point for checking if the number is even using the modulo operator %
  • +1 point for printing "Even" when the number is even
  • +1 point for printing "Odd" when the number is odd

Sample solution

public static void checkEvenOdd(int num) {
    if (num % 2 == 0) {
        System.out.println("Even");
    } else {
        System.out.println("Odd");
    }
}

Final Exam Focus

Alright, let's talk strategy for the big day. Here’s what to keep top of mind:

  • High-Value Topics:
    • Object-Oriented Programming (OOP): Classes, objects, inheritance, polymorphism. It's a biggie!
    • Arrays and ArrayLists: Manipulating and traversing data structures. Expect these!
    • Recursion: Understanding recursive methods and base cases. Tricky but important.
    • Sorting and Searching: Know the basic algorithms and their efficiency.
  • Common Question Types:
    • Code Tracing: Carefully follow code execution to predict output.
Exam Tip
  • Method Writing: Implement methods that solve specific problems.
Exam Tip
  • FRQs: Design and implement classes and methods.
Exam Tip
  • Last-Minute Tips:
    • Time Management: Don't get stuck on one question. Move on and come back if needed.
Exam Tip
  • Read Carefully: Pay close attention to instructions and constraints.
Exam Tip
  • Practice: Work through practice problems to build confidence.
Exam Tip
Quick Fact

Remember, you've got this! Stay calm, focused, and trust your preparation.

Previous Topic - If Statements and Control FlowNext Topic - Else If Statements

Question 1 of 8

What will be the output of the following code snippet? 🤔

int num = 7;
if (num < 5) {
  System.out.print("Small");
} else {
  System.out.print("Large");
}

Small

Large

Small Large

No output