Java Tutorial

Java Tutorial Java Features C++ vs Java Java History Java Hello World Java Development Kit Java Runtime Environment Java Virtual Machine Difference between JDK, JRE, and JVM Memory Areas in Java Java Operators Java Keywords Primitive Data Types Variables

Java Loops

Java Do While Loop Java While Loop Java For Loop Java Enhanced For Loop

Java Programs

Java Basic Programs Factorial Program in Java Fibonacci Series Program in Java Prime Number Program in Java Palindrome Number Program in Java Armstrong Number Program in Java Anagram Program in Java Pattern Programs in Java Calculator Program in Java Leap Year Program in Java Addition Program in Java Number Pattern Programs in Java Star Pattern Programs in Java Package Program in Java Pyramid Program in Java Sorting Program in Java String Palindrome Program in Java Even Odd Program in Java For Loop Program in Java If Else Program in Java Switch Case Program in Java GCD Program in Java LCM Program in Java Hello Program in Java Matrix Program in Java Menu Driven Program in Java Series Program in Java Client Server Program in Java Swapping Program in Java Pig Latin Program in Java Tower of Hanoi Program in Java Recursion Program in Java Matrix Multiplication Program in Java Perfect Number Program in Java Classes and Objects in Java Example Programs String Programs in Java Array Programs in Java Constructor Program in Java Inheritance Program in Java Abstract class Program in Java Interface Program in Java Encapsulation Program in Java Polymorphism Program in Java Exception Handling Program in Java Multithreading Program in Java Thread Program in Java Collection Programs in Java ArrayList Program in Java Stack Program in Java Applet Program in Java Swing Program in Java JDBC Program in Java How to run Java program in command prompt How to run Java program in Eclipse

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 inheritance with Example

Java inheritance Java inheritance is a mechanism in which a child object acquires all the properties and behaviors of a parent object. It helps in reusing the code and establishes a relationship between different classes. It is an essential part of oops (object-oriented programming system). As we know in real life, a son inherits the properties from his father just like that inheritance acts in Java. Java follows the similar concepts of son and father relationship. Java inheritance represents a parent-child relationship which is also known as IS-A relationship. Java has two classes

  • Parent class / Superclass / Base class
  • Child class/ Subclass /Derived class
A class whose properties are inherited is known as parent class whereas a class which inherits is known as Child class. Java uses the ‘extends’ keyword to inherit the attributes and methods from a class. Let’s have a look on the following example
class Teacher{
String prof = "Teacher";
String col_n = "IIT K";
void does(){
System.out.println("Teaching");
}
}
 public class CSTeacher extends Teacher{
     String sub = "Java";
     public static void main(String args[]){
     CSTeacher z = new CSTeacher();
     System.out.println(z.col_n);
     System.out.println(z.prof);
     System.out.println(z.sub);
     z.does();
       }
       }
Output
IIT K
Teacher
Java
Teaching
In the above example, the Child class CSTeacher holds the attributes and methods of parent class Teacher like designation, collegeName and void does(). The extends keyword indicates that you are using properties in a new class that derives from an existing class.

Advantage of Inheritance

  • Inheritance helps to achieve runtime polymorphism for method overloading.
  • Inheritance facilitates with code reusability.
  • Inheritance decreases the line of codes in Java program.
  • Inheritance minimizes the amount of duplicate code by sharing the standard code amongst several subclasses.
  • Inheritance facilitates with data hiding feature. The base class can decide to keep some data private so that the derived class can not alter it.

Disadvantage of Inheritance

The main disadvantage of inheritance is that two classes (base and derived) are tightly coupled that it cannot be used independently of each other. Another disadvantage of the inheritance is that it increases time/ effort it takes the program through all levels of overloaded class.

Types of inheritance in Java

Different types of inheritance supported by Java are as follows.
  • Single Inheritance
  • Multilevel Inheritance
  • Hierarchical inheritance

Single inheritance

In single inheritance, one class inherits only another class. Single Inheritence in Java with Example In the given figure, Class A is parent class, and Class B is Child Class, and class B is inheriting the properties and behavior. This process is known as single inheritance. Example
public class A
{
  public void print1()
  {
      System.out.println("Class A method");
  }
}
class B extends A
{
  public void print2()
  {
      System.out.println("Class B method");
  }
  public static void main(String[] args)
  {
      B d = new B();
      d.print1();
      d.print2();
      d.print1();
  } }
Output
Class A method
Class B method
Class A method 

Multilevel inheritance

In multilevel inheritance, a child class will be inheriting a parent class as well as the child class, and also parent class for some other class. In the given diagram, class A serves as a parent class for the class B., and also class B serves as a parent class for class C. This process is known as multilevel inheritance. A class can’t access directly inherit the grandparent class. Multiple Inheritence in Java
public class A
{
  public void print1()
  {
      System.out.println("Class A method");
  }
}
class B extends A
{
  public void print2()
  {
      System.out.println("Class B method");
  }
  }
class C extends B
{
    public void print3()
    {
        System.out.println("Class C method");
    }
public static void main(String[] args)
{
    C d = new C();
    d.print1();
    d.print2();
    d.print3();
}}
Output
Class A method
Class B method
Class C method

Hierarchical inheritance

In hierarchical inheritance, a single base class serves many sub classes. More than one child classes can inherit the properties of the parent class. java hierarchical inheritance In the given figure, Class B, Class C, and class D are the subclasses of Class A.

java hierarchical inheritance Example

class A
{
    public void print1()
    {
        System.out.println("Class A method");
    }
}
class B extends A
{
    public void print2()
    {
        System.out.println("Class B Method");
    }
}
class C extends A
{
     public void print3()
     {
          System.out.println("Class C method");
     }
}
public class Main
{
    public static void main(String[] args)
    {
        C d = new C();
        d.print1();
        B b = new B();
        b.print2();
        d.print3();
    }
}
Output
Class A method
Class B Method
Class C method

Super keyword in Java inheritance

In Java, the keyword ‘super’ and ‘this’ are very similar. Super keyword refers to the object of the base (parent) class. It acts as a reference variable. Super can be used in the following context.
  • Use of super with variables
  • Use of super with methods
  • Use of super with constructors

Some scenarios with the super keyword

Let’s see an example to understand the super keyword.   Example 1
class ParentClass
{
 int n = 50;
}
class ChildClass extends ParentClass
{
  int n = 80;
  void printNumber(){
     System.out.println(n);
  }
  public static void main(String args[]){
     ChildClass obj= new ChildClass();
     obj.printNumber();
  }
}
Output
80
In the given example, we have avoided the use of the super keyword. Now see the example with super keyword.
class ParentClass
{
 int n = 50;
}
class ChildClass extends ParentClass
{
  int n = 80;
  void printNumber(){
     System.out.println(super.n);
  }
  public static void main(String args[]){
     ChildClass obj= new ChildClass();
     obj.printNumber();
  }
}
Output
50
In the given example, when we use the super keyword then it refers the parent class object. Example 2 Let’s understand how super keyword acts with parent class constructor.
class ParentClass
{
    ParentClass()
    {
        System.out.println("Parent class Constructor");
    }
}
class ChildClass extends ParentClass
{
    ChildClass()
    {
        super(); //invoke super class constructor
        System.out.println("Child class Constructor");
    }
}
class SuperDemo
{
    public static void main(String[] args)
    {
        ChildClass c = new ChildClass();
    }
}
Output
Parent class Constructor
Child class Constructor
This is an example of use of super keyword with constructor.

Question: Does Java supports multiple inheritance, explain?

Answer Java doesn't support multiple inheritance through classes, but It can be achieved through interfaces. It has some conflict like the diamond problem that is why java developers excluded this feature from java. Multiple Inheritence Some other languages like c++, common lisp support multiple inheritance, but java avoids it. It prevents multiple inheritance from avoiding ambiguity.

Question: Explain diamond problem in Java.

Answer: The diamond problem The following diagram and program will clear the image of the diamond problem. diamond problem
class A
{
  void m1()
 {
System.out.println("class A");
}}
class B extends A
{
void m1()
{
System.out.println("Class B");
}
}
class C extends A
{
void m1()
{
 System.out.println("Class C");
}
}
class Test extends A, B
{
 public static void main(String args[])
 {
Test d1 = new Test();
 d1.m1();
 }
}
Output-
This program will produce compile time error.
As we can see in the above program on calling method m1() using D class object will cause complication. The program got confused whether it calls A's method m1() or B's method m1() because class D inheriting both class A and B. This complicated situation is called diamond problem.



ADVERTISEMENT
ADVERTISEMENT