JAVA Question Bank-1

1. What is transient variable?
Answer: Transient variable can't be serialize. For example if a variable is declared as transient in a Serializable class and the class is written to an ObjectStream, the value of the variable can't be written to the stream instead when the class is retrieved from the ObjectStream the value of the variable becomes null.

2. Name the containers which uses Border Layout as their default layout?
Answer: Containers which uses Border Layout as their default are: window, Frame and Dialog classes.

3. Is Iterator a Class or Interface? What is its use?
Answer: Iterator is an interface which is used to step through the elements of a Collection

4. Is Iterator a Class or Interface? What is its use?
Answer: Iterator is an interface which is used to step through the elements of a Collection

5. What is OOPS?
Answer: OOP is the common abbreviation for Object-Oriented Programming.

6. Describe the principles of OOPS.
Answer: There are three main principals of oops which are called Polymorphism, Inheritance and Encapsulation.

7. Explain the Inheritance principle.
Answer: Inheritance is the process by which one object acquires the properties of another
object.

8. Read the following program:
public class test {
public static void main(String [] args) {
int x = 3;
int y = 1;
if (x = y)
System.out.println("Not equal");
else
System.out.println("Equal");
}
}

What is the result?
A. The output is “Equal”
B. The output in “Not Equal”
C. An error at " if (x = y)" causes compilation to fall.
D. The program executes but no output is show on console.

9. Explain the Encapsulation principle.
Answer: Encapsulation is a process of binding or wrapping the data and the codes that operates on the data into a single entity. This keeps the data safe from outside interface and misuse. One way to think about encapsulation is as a protective wrapper that prevents code and data from being arbitrarily accessed by other code defined outside the wrapper.

10. Explain the different forms of Polymorphism.
Answer: From a practical programming viewpoint, polymorphism exists in three distinct forms in Java:
a. Method overloading
b. Method overriding through inheritance
c. Method overriding through the Java interface