Java Tutorial

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Java Loops

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Java Programs

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Java Sorting

Sorting Algorithms in Java Merge Sort in Java Quick Sort in Java Bubble Sort in Java Insertion Sort in Java Selection Sort in Java Heap Sort in Java Radix Sort in Java Topological Sort in Java Bucket Sort in Java Counting Sort in Java

Java OOPs Concepts

OOPs - Object Oriented Programming Objects and Classes in Java Java Naming Conventions Constructors in Java Java this keyword Java static keyword Inheritance in Java Aggregation in Java Java super keyword Constructor Chaining and Constructor Overloading Java Polymorphism Static and Dynamic Binding in Java Java Abstraction Abstract class in Java Interface in Java Difference between Abstract class and Interface Java final keyword Packages in Java Access Modifiers in Java Java Wrapper classes Java Numbers Java Characters Java Integer Java Boolean Java Arrays Java Command Line Arguments Java strictfp Keyword Java Math

Java Strings

Java Strings Java String Methods StringBuilder in Java StringBuffer in Java Java Regular Expressions StringBuffer vs StringBuilder String vs StringBuffer String vs StringBuilder String Manipulation in Java Java String Concatenation How to Reverse a String in Java String Array in Java How to Compare Two Strings in Java How to Concatenate Two Strings in Java Why String in Immutable in Java java.lang.NumberFormatException for Input String String Pool in Java Java Generate Random String How to take String Input in Java Java String Interview Questions

Java Exceptions

Exception Handling in Java Java try catch Java throw Java throws Difference between throw and throws Java finally Java Custom Exception Java Exception Propagation

Garbage Collection

Automatic Resource Management in Java Java Garbage Collection Java finalize() Java gc() Difference between final, finally and finalize

Multithreading

Multithreading in Java Process and Thread in Java Basic Terms in Multithreading Java Thread creation Thread Scheduler in Java Java Thread class DeadLock in Java

Java IO

Java IO Java Read File Java BufferedWriter Java InputStreamReader Java File Java Read File Line By Line Java FileOutputStream Jar File in Java

Serialization

Java Serialization Java transient

Networking

Java Network Programming Java Socket Programming Java URL Java URLConnection HttpURLConnection in Java Java InetAddress Java DatagramSocket and Java DatagramPacket

AWT

Java AWT

Swing

Swing in Java

Java Collections

Collections in Java Java List Interface ArrayList in Java LinkedList in Java Vector in Java Stack in Java ArrayList vs LinkedList in Java ArrayList vs Vector in Java Java Set Interface HashSet in Java LinkedHashSet in Java TreeSet in Java Java Queue Interface PriorityQueue in Java ArrayDeque in Java Java Map Interface HashMap in Java LinkedHashMap in Java TreeMap in Java Dictionary in Java Hashtable in Java Properties in Java Collections class in Java Java Comparable Java Comparator Comparable vs Comparator in Java

Java Generics

Generics in Java

Java Annotations

Annotations in Java

Java JDBC

Java JDBC Tutorial

Java Differences

Java vs JavaScript Python vs Java Kotlin vs Java Java vs C++ C# vs Java Static vs Non-static in Java C vs Java int vs Integer in Java Stack vs Heap in Java Java Array vs ArrayList

How to

How to run Java program How to set path in Java How to check the Java version in cmd How to install Java in Windows 10 How to run Java program in cmd How to call a method in Java How to sort an array in Java How to iterate HashMap in Java How to write Java program How to create an array in Java How to create a package in Java How to generate random numbers in Java How to input String in Java How to create thread in Java How to find length of String in Java How to sort a string in Java How to use scanner in Java How to achieve multiple inheritance in Java How to run Java program in Eclipse How to call a function in Java How to create array of objects in Java How to create custom exception in Java How to achieve abstraction in Java How to call static method in Java

Java 8 Features

Java 8 Features Lambda Expressions in Java Functional Interface in Java Streams in Java Java Base64 Encoding and Decoding Parallel Arrays Sort in Java

Java 9 Features

Java 9 Tutorial Java 9 Try With Resources Java 9 Interface Private Method

Java Servlet Tutorial

Java Servlets Tutorial

Java JSP Tutorial

Java JSP Tutorial

Hibernate Tutorial

Hibernate Tutorial

Spring Tutorial

Spring Tutorial

Spring MVC Tutorial

Spring MVC Tutorial

Jenkins Tutorial

Jenkins Tutorial

Java Math Methods

Math.abs() Math.acos() Math.addExact() Math.asin() Math.atan () Math.atan2() Math.cbrt() Math.ceil() Math.copysign() Math.cos() Math.cosh() Math.decrementExact() Math.exp() Math.expm1() Math.floor() Math.floorDiv() Math.floorMod() Math.getExponent() Math.hypot() Math.IEEEremainder() Math.incrementExact() Math.log() Math.log10() Math.log1p() Math.max() Math.min() Math.multiplyExact() Math.multiplyFull() Math.negateExact() Math.nextAfter() Math.nextDown() Math.nextUp() Math.pow() Math.random() Math.rint() Math.round() Math.scalb() Math.signum() Math.sin() Math.sinh() Math.sqrt() Math.subtractExact() Math.tan() Math.tanh() Math.toDegrees() Math.toIntExact() Math.toRadians() Math.ulp()

Java String Methods

toCharArray() copyValueOf() endsWith() equals() equalsIgnoreCase() format() getBytes() getChars() hashCode() indexOf() intern() isEmpty() join() lastIndexOf() length() replace() replaceAll() replaceFirst() split() startsWith() subSequence() substring() toLowerCase() toUpperCase() trim() valueOf()

Java Conversion

Java Convert String to int Java Convert int to String Java Convert String to long Java Convert long to String Java Convert String to float Java Convert float to String Java Convert String to double Java Convert double to String Java Convert String to Date Java Convert Date to String Java Convert String to Object Java Convert Object to String Java Convert String to char Java Convert char to String Java Convert int to long Java Convert long to int

Misc

Functional Interfaces in Java Singleton class in Java Awesome explanation of Strings in Java Object class in Java Static class in Java All the important string methods in Java String Handling Method in Java What are Array strings in Java Advantages and Disadvantages of Strings in Java Big Decimal class in Java Class definition in Java Char and String differences in Java Difference between String, StringBuffer and StringBuilder in java Replace character in string Java String Coding Interview Questions in Java What is String in Java? String isnullorempty in Java String Matches in Java Trim Method in String Java Bean class in Java Libraries in Java Arithmetic Operations on String in Java Convert Char array to string in java Check whether Java is installed or not How to calculate time difference in Java How to stop execution after a certain time in Java Jagged Array in Java Java ArraylistRemove() Time Complexity Java Swing Time Picker Zigzag Array in Java

Java Polymorphism

The process of representing one form in multiple forms is known as Polymorphism.

Polymorphism is derived from 2 Greek words: poly and morphs. The word "poly" means many and "morphs" means forms. So polymorphism means many forms.

Polymorphism is not a programming concept, but it is one of the principals of OOPs. For many objects oriented programming language, polymorphism principle is common but whose implementations are varying from one objects oriented programming language to another object-oriented programming language.

Real life example of polymorphism

Suppose if you are in a classroom that time you behave like a student, when you are in the market at that time you behave like a customer, when you at your home at that time you behave like a son or daughter, Here one person present in different-different behaviors.

How to achieve Polymorphism in Java?

Polymorphism can be achieved in two of the following ways:

  • Method Overloading(Compile time Polymorphism)
  • Method Overriding(Run time Polymorphism)

Polymorphism principal is divided into two sub-principal they are:

  • Static or Compile time polymorphism
  • Dynamic or Runtime polymorphism

Static polymorphism in Java is achieved by method overloading, and Dynamic polymorphism in Java is achieved by method overriding

Note: Java programming does not support static polymorphism because of its limitations and java always supports dynamic polymorphism.

Example of Runtime Polymorphism in Java

In below example we create two class Person an Employee, Employee class extends Person class feature and override walk() method. We are calling the walk() method by the reference variable of Parent class. Since it refers to the subclass object and the subclass method overrides the Parent class method, the subclass method is invoked at runtime. Here method invocation is determined by the JVM not compiler, So it is known as runtime polymorphism.

Example of Polymorphism in Java

class Person
{
void walk()
{
System.out.println("Can Run....");
}
}
class Employee extends Person
{
void walk()
{
System.out.println("Running Fast...");
}
public static void main(String arg[])
{
Person p=new Employee(); //upcasting
p.walk();
}
}

Output

Running fast...

Dynamic Binding

Dynamic binding always says create an object of base class but do not create the object of derived classes. Dynamic binding principal is always used for executing polymorphic applications.

The process of binding appropriate versions (overridden method) of derived classes which are inherited from the base class with the base class object is known as dynamic binding.

Advantages of dynamic binding along with polymorphism with method overriding are.

  • Less memory space
  • Less execution time
  • More performance

Static polymorphism

The process of binding the overloaded method within the object at compile time is known as Static polymorphism due to static polymorphism utilization of resources (main memory space) is poor because for each and every overloaded method a memory space is created at compile time when it binds with an object. In C++ environment the above problem can be solved by using dynamic polymorphism by implementing with virtual and pure virtual function, so most of the C++ developer in real worlds follows only dynamic polymorphism.

Dynamic polymorphism

In dynamic polymorphism method of the program binds with an object at runtime the advantage of dynamic polymorphism is allocating the memory space for the method (either for the overloaded method or for override method) at run time.

The advantage of dynamic polymorphism is the effective utilization of the resources. So Java always uses dynamic polymorphism. Java does not support static polymorphism because of its limitation.

Form of Polymorphism

There are many forms of polymorphism,

  • Polymorphism with class
  • Polymorphism in methods
  • Polymorphism in interface

Polymorphism with classes

Those Java classes that can pass more than one IS-A test is polymorphic in nature. All Java classes are derived from the object class so, its references can pass the instance of operator test with the object class and its own object. So, we can conclude that all Java class is polymorphic.

We can access the objects in Java through a reference variable. These reference variables can assign different objects (if reference is not declared final) also once declared, and these references type cannot be changed.

The reference variable determines which method it can invoke on the object. The reference variable can be declared as a class or interface type. A reference variable can refer to any object of the declared type or its subtype.

Example:

abstract class Animal {
public void run() {
System.out.println("Run fast...");
}
public abstract void eat();
}
class Lion extends Animal {
public void eat() {
System.out.println("Catch deer and eat");
}
}
class Deer extends Animal {
public void eat() {
System.out.println("Search grass and eat ");
}
}
class Testpolymorphism {
public static void main(String[] args) {
Animal animal1 = new Lion();
Animal animal2 = new Deer();
animal1.run();
animal2.run();
animal1.eat();
animal2.eat();
}
}

Output:

Run fast...
Run fast...
Catch deer and eat
Search grass and eat

In method Overriding, JRE decides which method is to invoke in run time, based on the exact type of the object on which the method is called.

Polymorphism in methods (Binding of variables and methods at compile time and runtime)

Binding refers to resolving variables or methods that would be called for a reference variable. We use a reference variable of a base class to refer to an object of a derived class.

But there is a difference. Instance variables bind at compile time while the methods bind at runtime.

Example:

class Parent {
String name = "Gopal";
void displayName() {
System.out.println("Name is " + name);
}
}
class Child extends Parent {
String name = "Rohan";
void displayName() {
System.out.println("Name is " + name);
}
}
public class DynamicBinding {
public static void main(String[] args) {
Parent a = new Parent();
Parent b = new Child();
System.out.println(a.name);
System.out.println(b.name);
a.displayName();
b.displayName();
}
}

Output:

Gopal
Gopal
Name is Gopal
Name is Rohan

System.out.println(b.name); will print Gopal since the reference variable is of type Parent. The field variable binds at the compile time.

b.displayName(); will print the name Rohan because JRE sees that the exact object is of type Child and have an overriding method displayName hence, JRE invokes the displayName of the Child Class.

Polymorphism with interfaces

We can implement polymorphism using interface also. We need a class which implements this interface.

Polymorphism with interfaces involves abstract or default methods of the interface. The interface can also define static methods, but static methods never participate in polymorphism.

Example :

class Parent implements PlayGames {
public void play() {
System.out.println("Don't play games");
}
}
class Child extends Parent implements PlayGames {
public void play() {
System.out.println("Always want to play games");
}
}
interface PlayGames {
void play();
}
public class DynamicBinding2 {
public static void main(String[] args) {
PlayGames a = new Parent();
PlayGames b = new Child();
a.play();
b.play();
}
}

Output:

Don't play games
Always want to play games

JRE dynamically calls the method of the corresponding object and executes their methods.



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