Java

Question 1

Types of inheritance

Answer 1

Single
multilevel
hierarchical
hybrid
multiple(doesn’t support)

Question 2

jDK (java development kit)

Answer 2

It’s a package that includes the JRE, plus tools for developing, debugging, and monitoring Java applications.

Question 3

JRE (Java Runtime Environment):

Answer 3

It includes the JVM along with libraries and other components needed to run Java applications.

run a Java program on your computer, you need the JRE installed.

Question 4

JVM (Java Virtual Machine)

Answer 4

JVM is a Java Virtual Machine which is a run time environment for the compiled java class files.

Converts bytecode to machine readable code

Question 5

JIT(Just-in-Time) Compiler

Answer 5

It is a part of JRE(Java Runtime
Environment), it is used for better performance of the Java applications
during run-time.

Question 6

Latest version of java

Answer 6

Java 22 & jDK 22

Question 7

Who developed Java ?

Answer 7

James Gosling at Sun Microsystems

Question 8

when was java released?

Answer 8

May 1995

Question 9

Features of java

Answer 9

1.Platform independent
2.Simple and easy to learn
3.Object oriented
4.Robust and secure
5.Automatic Garbage Collection
6.High Performance
7.Multithreading

Question 10

When was Jvm 1.0 released?

Answer 10

JDK 1.0 was released on January 23 1996.

Question 11

Garbage collection

Answer 11

Garbage collection is the
automatic process of identifying
and reclaiming memory occupied
by objects that are no longer
referenced.
Java uses different
garbage collection algorithms like
generational, mark-and-sweep,
and G1.

Question 12

Garbage value

Answer 12

The Garbage value isa random value at an address in the memory of a computer. It is leftover values from previous program

Question 13

What is the Java Collections Framework, and why
is it important?

Answer 13

The Java Collections Framework provides a set of classes and interfaces
for working with collections of objects. It’s essential for efficient data
manipulation and storage in Java applications

Question 14

Difference between arrraylist and linklist

Answer 14

ArrayList is a dynamic array that allows fast random access, while
LinkedList is a doubly-linked list that is better suited for frequent insertions
and deletions.

Question 15

Explain the ‘finalize()’ method in Java.

Answer 15

‘finalize()’ is a method called by the garbage collector before an object is
reclaimed. It allows you to perform cleanup operations on resources like
files or sockets.

Question 16

Describe the ‘enum’ type in Java and its
advantages.

Answer 16

An ‘enum’ is a special data type that defines a set of constant values. It
provides type safety, readability, and can be used in switch statements.

Question 17

What is the ‘autoboxing’ and ‘unboxing’ feature in
Java?

Answer 17

Autoboxing is the automatic conversion of a primitive type to its
corresponding wrapper class, and unboxing is the reverse process.

For example, converting ‘int’ to ‘Integer’ and vice versa.

Question 18

What are Java annotations, and how are they used?

Answer 18

Annotations provide metadata about the code and can be used to add
information to classes, methods, or variables. They are commonly used for
configuration, documentation, and code generation.

Question 19

What is an exception in java?

Answer 19

In java, an exception is an object. Exceptions are created when abnormal situations arise in our program.
Exceptions can be created by JVM or by our application code.

Question 20

Why doesn’t it support multiple inheritances?

Answer 20

Because of the “Diamond Problem”, Java doesn’t support multiple inheritances in classes.

Question 21

In how many ways we can do exception handling in java?

Answer 21

We can handle exceptions in either of the two ways :
1) By specifying a try-catch block where we can catch the exception.
2) Declaring a method with a throw clause.

Question 22

Why is Java not a pure object oriented language?

Answer 22

Java supports primitive data types - byte, boolean, char, short, int, float, long, and
double and hence it is not a pure object oriented language.

Question 23

How is Java different from C++?

Answer 23

C++ is only a compiled language, whereas Java is compiled as well as an
interpreted language.
Java programs are machine-independent whereas a c++ program can run only in
the machine in which it is compiled.
C++ allows users to use pointers in the program.
Whereas java doesn’t allow it.
Java internally uses pointers.

Question 24

Can you tell the difference between equals() method and
equality operator (==) in Java?

Answer 24

equals()
This is a method defined
in the Object class.
It is a binary operator in Java.
This method is used for
checking the equality of
contents between two
objects as per the
specified business logic.

==

This operator is used for
comparing addresses (or
references), i.e checks if both
the objects are pointing to the
same memory location.

It a binary operator in java

Question 25

Can the main method be Overloaded?

Answer 25

Yes, It is possible to overload the main method. We can create as many overloaded
main methods we want. However, JVM has a predefined calling method that JVM will
only call the main method with the definition of -
public static void main(string[] args)

Question 26

Difference between static methods, static variables, and
static classes in java??

Answer 26

Static Methods and Static variables are those methods and variables that
belong to the class of the java program, not to the object of the class. This gets
memory where the class is loaded. And these can directly be called with the help
of class names.