AP Computer Science A Unit 2 Review

AP Computer Science A Unit 2 Review with Java Code…

1. Objects – Instances of Classes

public class Dog {
    String breed; // Breed of the dog
    int age;      // Age of the dog
    
    void bark() {
        System.out.println("Woof!"); // Print bark sound
    }
}

public class ObjectExample {
    public static void main(String[] args) {
        // Creating an object of a class
        Dog myDog = new Dog();
        
        // Accessing and modifying object's properties
        myDog.breed = "Labrador";
        myDog.age = 3;
        
        // Calling object's methods
        myDog.bark();
    }
}

2. Creating and Storing Objects (Instantiation)

public class ObjectInstantiationExample {
    public static void main(String[] args) {
        // Instantiating an object using the 'new' keyword
        Dog myDog = new Dog();
        
        // Storing the created object in a variable
        Dog anotherDog = myDog;
    }
}

3. Calling a Void Method

public class VoidMethodExample {
    public static void main(String[] args) {
        Dog myDog = new Dog();
        myDog.bark(); // Calling a void method
    }
}

4. Calling a Void Method with Parameters

public class VoidMethodWithParametersExample {
    public static void main(String[] args) {
        Dog myDog = new Dog();
        myDog.feed("bones"); // Calling a void method with parameters
    }
}

5. Calling a Non-void Method

public class NonVoidMethodExample {
    public static void main(String[] args) {
        Dog myDog = new Dog();
        int dogAge = myDog.getAge(); // Calling a non-void method
    }
}

6. String Objects – Concatenation, Literals, and More

public class StringExample {
    public static void main(String[] args) {
        // Concatenating string objects
        String fullName = "John" + " " + "Doe";
        
        // String literals
        String message = "Hello, World!";
    }
}

7. String Methods

public class StringMethodsExample {
    public static void main(String[] args) {
        String str = "Hello, World!";
        
        // Using string methods
        int length = str.length();
        char firstChar = str.charAt(0);
        String subStr = str.substring(0, 5);
    }
}

8. Wrapper Classes – Integer and Double

public class WrapperClassExample {
    public static void main(String[] args) {
        // Using wrapper classes
        Integer intObject = Integer.valueOf(5);
        Double doubleObject = Double.valueOf(3.14);
    }
}

9. Using the Math Class

public class MathExample {
    public static void main(String[] args) {
        // Using methods of the Math class
        double pi = Math.PI;
        double sqrtValue = Math.sqrt(16);
    }
}