Java Interview Questions Cheat Sheet

by sdm7306 via cheatography.com/51374/cs/14061/

Main Features of Java

Object Oriented

Simple

Platform Independent

Secure

Robust

Portable

Multithreaded

Distributed

Principles of OOP

Abstr

action

Abstraction means using simple

things to represent complexity using

object, classes, and variables.

Encap

sulati

This is the practice of keeping fields

within a class private, then providing

access to them via public methods.

It’s a protective barrier that keeps the

data and code safe within the class

itself.

Inherit

ance

It lets programmers create new

classes that share some of the

attributes of existing classes. This lets

us build on previous work without

reinventing the wheel.

Polym

orphis

Polymorphism refers to any entity

whether it is a method or a

constructor or an operator which takes

many forms or can be used for

multiple tasks.

Multithreaded Programming

Multithreaded programming is one of the key

features of java which allows multiple threads

to execute their task simultaneously.

There are two ways to create threads in

Java

a) by extending the Thread class

b) by implementing the Runnable interface

Final, Finally, Finalize

Final Makes a variable, method, or class

unchangeable.

Final

Exception handling after success or

failure during a try catch block.

Final

ize

Called by the garbage collector on an

object when garbage collection

determines that there are no more

references to the object.

Inheritance

Inheritance is one of the key principle of object

oriented programming. Through inheritance,

one class can inherit the properties of another

class. The class from which properties are

inherited is called super class and the class to

which properties are inherited is called sub

class.

Does Java support multiple inheritance?

Java supports multiple inheritance but only

through interfaces. That means a class can

implement more than one interfaces but can

not extend more than one class.

Constructor & Method Overloading

A class can have any number of constructors.

These constructors will have different list of

arguments. It is called constructor

overloading. Constructor overloading provides

different ways to instantiate a class.

If a class has more than one method with same

name but with different list of arguments, then it

is called method overloading.

Overriding

If a super class method is modified in the sub

class then it is called method overriding.

Abstract Classes

An abstract class is a class which cannot be

instantiated. An abstract class is used by

creating an inheriting subclass that can be

instantiated. An abstract class does a few

things for the inheriting subclass:

1.Define methods which can be used by the

inheriting subclass.

2.Define abstract methods which the inh eriting

subclass must implement.

3.Provide a common interface which all ows the

subclass to be interchanged with all other

subclasses.

Exception Handling

try The code to be monitored for

exceptions will be kept in this block.

catch If any exceptions occurred in try block,

those exceptions will be caught by this

block.

finall

This block will be always executed

whether exception is raised or not and

raised exceptions are caught or not.

Checked & Unchecked Exceptions

Checked Known and checked at compile

time.

Uncheck

Known at Runtime, unknown at

compile time.

Static & Non-Static Methods

Static method is common to all instances of a

class. Static methods are stored in the class

memory. Where as non-s



tatic methods are

stored in the object memory. Each instance of a

class will have their own copy of non-static

methods.

Synchronization

Synchronization is a way of controlling the

access of a method or a block by multiple

threads. Only one thread can enter into a

method or a block which has been declared as

synchronized. Synchronization is one of the

way to achieve thread safety.

By sdm7306

cheatography.com/sdm7306/

Published 21st December, 2017.

Last updated 21st December, 2017.

Page 1 of 2.

Download Java Interview Questions Cheat Sheet and more Cheat Sheet Java Programming in PDF only on Docsity!

Java Interview Questions Cheat Sheet

by sdm7306 via cheatography.com/51374/cs/14061/

Main Features of Java Object Oriented Simple Platform Independent Secure Robust Portable Multithreaded Distributed Principles of OOP Abstr action Abstraction means using simple things to represent complexity using object, classes, and variables. Encap sulati on This is the practice of keeping fields within a class private, then providing access to them via public methods. It’s a protective barrier that keeps the data and code safe within the class itself. Inherit ance It lets programmers create new classes that share some of the attributes of existing classes. This lets us build on previous work without reinventing the wheel. Polym orphis m Polymorphism refers to any entity whether it is a method or a constructor or an operator which takes many forms or can be used for multiple tasks. Multithreaded Programming Multithreaded programming is one of the key features of java which allows multiple threads to execute their task simultaneously. There are two ways to create threads in Java a) by extending the Thread class b) by implementing the Runnable interface Final, Finally, Finalize Final Makes a variable, method, or class unchangeable. Final ly Exception handling after success or failure during a try catch block. Final ize Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. Inheritance Inheritance is one of the key principle of object oriented programming. Through inheritance, one class can inherit the properties of another class. The class from which properties are inherited is called super class and the class to which properties are inherited is called sub class. Does Java support multiple inheritance? Java supports multiple inheritance but only through interfaces. That means a class can implement more than one interfaces but can not extend more than one class. Constructor & Method Overloading A class can have any number of constructors. These constructors will have different list of arguments. It is called constructor overloading. Constructor overloading provides different ways to instantiate a class. If a class has more than one method with same name but with different list of arguments, then it is called method overloading. Overriding If a super class method is modified in the sub class then it is called method overriding. Abstract Classes An abstract class is a class which cannot be instantiated. An abstract class is used by creating an inheriting subclass that can be instantiated. An abstract class does a few things for the inheriting subclass:

1. Define methods which can be used by the inheriting subclass. 2. Define abstract methods which the inheriting subclass must implement. 3. Provide a common interface which allows the subclass to be interchanged with all other subclasses. Exception Handling try The code to be monitored for exceptions will be kept in this block. catch If any exceptions occurred in try block, those exceptions will be caught by this block. finall y This block will be always executed whether exception is raised or not and raised exceptions are caught or not. Checked & Unchecked Exceptions Checked Known and checked at compile time. Uncheck ed Known at Runtime, unknown at compile time. Static & Non-Static Methods Static method is common to all instances of a class. Static methods are stored in the class memory. Where as non-static methods are stored in the object memory. Each instance of a class will have their own copy of non-static methods. Synchronization Synchronization is a way of controlling the access of a method or a block by multiple threads. Only one thread can enter into a method or a block which has been declared as synchronized. Synchronization is one of the way to achieve thread safety. By sdm cheatography.com/sdm7306/ Published 21st December, 2017. Last updated 21st December, 2017. Page 1 of 2. Sponsored by CrosswordCheats.com Learn to solve cryptic crosswords! http://crosswordcheats.com

Java Interview Questions Cheat Sheet

by sdm7306 via cheatography.com/51374/cs/14061/

Garbage Collection Removing unwanted objects or abandoned objects from the memory is called garbage collection. Garbage collection is done automatically in java. You need not to remove the unwanted objects explicitly. Garbage collector thread does this for you. Cloning Cloning is a process of creating an exact copy of an existing object in the memory. Cloning may be shallow or deep. In java, clone() method is used to create a clone of an object. Interfaces A Java interface is a bit like a class, except a Java interface can only contain method signatures and fields. An Java interface cannot contain an implementation of the methods, only the signature (name, parameters and exceptions) of the method. You can use interfaces in Java as a way to achieve polymorphism. By sdm cheatography.com/sdm7306/ Published 21st December, 2017. Last updated 21st December, 2017. Page 2 of 2. Sponsored by CrosswordCheats.com Learn to solve cryptic crosswords! http://crosswordcheats.com

Java Interview Questions Cheat Sheet, Cheat Sheet of Java Programming

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Download Java Interview Questions Cheat Sheet and more Cheat Sheet Java Programming in PDF only on Docsity!

Java Interview Questions Cheat Sheet

by sdm7306 via cheatography.com/51374/cs/14061/

Java Interview Questions Cheat Sheet

by sdm7306 via cheatography.com/51374/cs/14061/