Java Study Questions and Answers: Test Your Knowledge with Practical Examples

Java Study Questions and Answers
1. What is Java?
Answer:
Java is a high-level, object-oriented programming language developed by James
Gosling at Sun Microsystems (now owned by Oracle). It follows the "Write Once,
Run Anywhere" philosophy, meaning code written in Java can run on any platform
that supports a Java Virtual Machine (JVM). Java is widely used for building web
applications, mobile applications (Android), and enterprise-level systems.



2. What are the different types of data types in Java?
Answer:
Java has two main types of data types:

 Primitive Data Types:
o byte: 8-bit integer
o short: 16-bit integer
o int: 32-bit integer
o long: 64-bit integer
o float: 32-bit floating point
o double: 64-bit floating point
o char: 16-bit Unicode character
o boolean: true or false
 Non-Primitive Data Types:
o String: A sequence of characters.
o Array: A collection of similar data types.
o Object: An instance of a class, which can hold multiple values and
methods.

, 3. What is the difference between == and equals() in Java?
Answer:

 == is a reference comparison operator used to check if two references point
to the same object in memory (it checks for object identity).
 equals() is a method defined in the Object class, which is used to compare
the actual content or state of two objects for equality.

Example:

String str1 = new String("Hello");
String str2 = new String("Hello");

System.out.println(str1 == str2); // false (different objects)
System.out.println(str1.equals(str2)); // true (same content)



4. What is inheritance in Java?
Answer:
Inheritance is an OOP concept in Java that allows one class to inherit fields and
methods from another class. The class that inherits is called the subclass or child
class, and the class it inherits from is called the superclass or parent class. It helps
to achieve code reusability and method overriding.

Example:

class Animal {
void sound() {
System.out.println("Animal makes a sound");
}
}

class Dog extends Animal {
void sound() {
System.out.println("Dog barks");