Java Unit 1

Which of the following is NOT an OOP principle?

• Encapsulation
  

• Abstraction
  

• Compilation
  

• Inheritance

What is an object in Java?

• a) A variable
  

• b) An instance of a class
  

• c) A function
  

• d) A primitive data type

What is the main purpose of encapsulation?

• a) To allow direct access to all variables
  

• b) To hide the implementation details of a class
  

• c) To inherit properties from another class
  

• d) To create multiple objects

What is polymorphism in Java?

• a) Multiple classes with the same name
  

• b) Ability of a variable to hold multiple types
  

• c) Ability of a method to behave differently based on the object calling it
  

• d) The use of multiple objects in a program

Which of the following is NOT a characteristic of Java?

• a) Platform independent
  

• b) Supports multiple inheritance through classes
  

• c) Object-oriented
  

• d) Secure

What is the Java Virtual Machine (JVM)?

• a) A compiler
  

• b) A runtime environment for Java programs
  

• c) A debugger
  

• d) An integrated development environment

What is the correct syntax for a single-line comment in Java?

• a) /* comment */
  

• b) // comment
  
  

• c) -- comment

• d) # comment

Which statement is used to exit a method and return a value?

• a) continue
  

• b) break
  

• c) return
  

• d) exit

Which of the following statements about method overriding and method overloading in Java is correct?

• a) Method overloading allows a subclass to redefine a method from its superclass.
  
  

• b) Method overriding requires that the method signatures in the superclass and subclass be different.

• c) Method overloading occurs when two or more methods in the same class have the same name but different parameter lists.
  

• d) Method overriding can be done within the same class.

What is the output of the following Java program?

class Test {

final int x;

Test() {

x = 10;

}

void changeValue() {

x = 20; // Line A

}

public static void main(String[] args) {

Test obj = new Test();

obj.changeValue();

}

}

• Compilation error
• Runtime error
• Output: 20
• Output: 10