Key Points and Sample Codes

1. Objects: Instances of Classes (2.1)
• Key Points: Objects are instances of classes, encapsulating data and methods that operate on data.
• Sample Code:

2. Creating and Storing Objects (Instantiation) (2.2)
• Key Points: Objects are created using the new keyword and stored in variables.
• Sample Code:

3. Calling a Void Method (2.3)
• Key Points: Void methods perform actions but do not return a value.
• Sample Code:

4. Calling a Void Method with Parameters (2.4)
• Key Points: Methods can accept parameters to customize their behavior.
• Sample Code:

5. Calling a Non-void Method (2.5)
• Key Points: Non-void methods return a value.
• Sample Code:

6. String Objects: Concatenation, Literals, and More (2.6)
• Key Points: Strings can be concatenated using +, and literals are defined using double quotes.
• Sample Code:

7. String Methods (2.7)
• Key Points: String class provides methods like length(), substring(), indexOf().
• Sample Code:

8. Wrapper Classes: Integer and Double (2.8)
• Key Points: Wrapper classes provide a way to use primitive data types as objects.
• Sample Code:

9. Using the Math Class (2.9)
• Key Points: The Math class provides methods for performing basic numeric operations such as the elementary exponential, logarithm, square root, and trigonometric functions.
• Sample Code:

20 AP Style MCQs

1. Which of the following is used to create a new object in Java?
• A) new
• B) class
• C) newClass
• D) instance

2. What will the following code print?
• A) Test
• B) obj
• C) Hello World
• D) Nothing

3. What is the output of the following code?
• A) Java Programming
• B) JavaProgramming
• C) Java
• D) Programming

4. What does the following method return type signify?
• A) Returns an integer
• B) Returns nothing
• C) Returns a string
• D) Returns a boolean

5. Which method would you use to determine the length of the string "APCSA"?
• A) getLength()
• B) length()
• C) size()
• D) lengthOf()

6. What will be the output of the following Java code snippet?
• A) True
• B) False
• C) Error
• D) None of the above

7. What is the result of the following expression in Java?
• A) 6
• B) 8
• C) 5
• D) 9

8. In Java, which of the following can be used to concatenate two strings?
• A) +
• B) append()
• C) concatenate()
• D) attach()

9. How can you create a string that represents the name "John Doe" using string literals?
• A) String name = "John" + "Doe";
• B) String name = "John" + " " + "Doe";
• C) String name = "John, Doe";
• D) String name = "John-Doe";

10. Which method of the String class returns the position of the first occurrence of a specified character string in a String?
• A) find()
• B) search()
• C) locate()
• D) indexOf()

11. Consider the following Java class:
What is the correct way to call the start method on an object of Vehicle named myCar?
• A) Vehicle.start();
• B) Vehicle myCar = start();
• C) myCar.start();
• D) start(myCar);

12. If you create a String object as follows:
What is the result of greeting.length()?
• A) 12
• B) 13
• C) 14
• D) An error occurs

13. Which of the following code snippets correctly creates an Integer object representing the number 42?
• A) Integer num = new Integer("42");
• B) Integer num = Integer.valueOf("42");
• C) Integer num = 42;
• D) All of the above

14. What is the return type of the Math.abs() method when passed an integer argument?
• A) int
• B) double
• C) long
• D) float

15. What is the purpose of the void keyword in a method declaration?
• A) Indicates that the method returns no value
• B) Declares a variable inside the method
• C) Makes the method invisible to other classes
• D) None of the above

16. Which of the following is a correct way to use the Math.random() method to generate a random integer between 0 and 99?
• A) (int) (Math.random() * 100)
• B) (int) (Math.random() * 99)
• C) (Math.random() * 99)
• D) Math.random(100)

17. In Java, what does the String method substring(1, 4) return when called on the string "example"?
• A) "xam"
• B) "xamp"
• C) "exam"
• D) "xample"

18. What will be the result of executing the following code segment?
• A) true
• B) false
• C) Error
• D) None of the above

19. How can you convert a double to a String in Java?
• A) String.valueOf(double)
• B) Double.toString(double)
• C) double.toString()
• D) Both A and B are correct

20. Which wrapper class method is used to parse a String into an Integer?
• A) Integer.parseInt()
• B) Integer.valueOf()
• C) Integer.toString()
• D) Integer.parseString()