Java Tutorial

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Java Loops

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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

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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 Thread Creation

Java provides the two ways to create a Thread:

  • Implementing the Runnable interface.
  • Extending the Thread class.

Implementing Runnable interface

The easiest way of creating a thread is to make a class that implements the Runnable interface. The runnable interface represents a unit of executable code. We can create a thread on the object which implements Runnable. A class only implements a single method called run() if it implements the Runnable interface.

We will define the code in the run method of the Runnable interface that constitutes the new thread. The run() can call other methods of the class, can use other classes, and declare variables. The run() establishes the entry point for the execution of the thread within your program. The thread will end when run() finishes.

We can instantiate an object of type Thread in which a class that implements Runnable is passed so that we can start the new thread. Thread has a constructor that we will use to start the run method of the Thread class.

Syntax:

Thread(Runnable r1,
String tname)

In this constructor, r1 is an instance of a class that implements the Runnable interface, and tname is the name of the new thread. When the new thread is created, it will start running when you call its start() method, which is declared within Thread.

Steps for creating a new thread using Runnable:

Step1: Create a Runnable implemented class and implements the run() method.

Step2: Instantiate Thread class and pass the Runnable implemented class to the Thread, Thread has a constructor which accepts Runnable implementer instance.

Step3: Invoke start() of Thread instance, start()  internally calls run() of the implemented class. By invoking start() creates a new Thread, which executes the code written in the run().

Example1: Creating the thread using the Runnable interface.

class Thread2 implements Runnable{
 Thread t;
 Thread2(){
 //create a new,second thread.
 t=new Thread(this, "Shifa-thread"); 
 System.out.println("The child thread is the  :"+t);
 t.start();//we are starting the thread.
 }
 //this is the entry point for  execution of the second thread. 
 public void run()
 {
 try
 {
 for(int i1=5;i1>0;i1--) 
 {
 System.out.println("child thread:"+i1);
 Thread.sleep(500);
 }
 }catch(InterruptedException ex) 
 {
 ex.printStackTrace();
 }
 System.out.println("The exiting child thread is the"); 
 }
 }
 public class Multithread{
 public static void main(String[] args) { 
 new Thread2();//create a new thread.
 try
 {
 for(int i=5;i>0;i--) 
 {
 System.out.println("Main thread:"+i);
 Thread.sleep(1000);
 } 
 }catch(InterruptedException e) {
 e.printStackTrace();
 System.out.println("Main thread interrupted");
 }
 System.out.println("Main thread exiting");
 }
 } 

Output:

Java Thread Creation

Explanation:

In the Thread2 class ‘s constructor, a new Thread object is created by the following statement:

t=new Thread(this, "Shifa thread");

when start()method calls ,this cause the child thread’s for loop to begin. When the main resume its execution it enters into the loop. Then both sharing the cpu until their loops finish.

Creating the thread by extending the Thread class

A thread class can also make by extending the predefined Thread class, and then to instantiate that class. The entry point run() method for the new thread, must be overridden in the extended class. Here is the preceding program was rewritten to extend Thread.

Steps to create a new thread using Thread class:

Step1: Create a Thread extended class and overriding run() method of the Thread class according to your requirements.

Step2: Instantiate Thread extended class.

Step3: Invoke start() of Thread class through the instance of the Thread extended class, start() internally calls run() method which overrides in the user class. The whole activities of the thread which is defined in the run() executes.

Example1: Create the thread using the Thread class.

class Thread3 extends Thread{
 Thread3(){
 super("Demo Thread");
 System.out.println("child thread:"+this);
 start();//start the thread. This is equivalent to this.start().
 } 
 //The run() is the entry point for the second thread.
 public void run()
 {
 try
 {
 for(int i1=5;i1>0;i1--) 
 { 
 System.out.println("child thread:"+i1);
 Thread.sleep(500);
 }
 } 
 catch(InterruptedException ex)
 {
 ex.printStackTrace();
 }
 }
 } 
 public class Multithread { 
 public static void main(String args[]) 
  { 
 new Thread3();//create a new thread.
 try 
 {
  for(int i=5;i>0;i--)
 {
  System.out.println("Main thread:"+i); 
  Thread.sleep(1000);
  }
 }catch(InterruptedException e) 
 { 
 System.out.println("Main thread interrupted");
 } 
 System.out.println("Main thread exiting"); 
 }  
 } 

Output:

Java Thread Creation2

Explanation:

The thread of the child is created by creating the object of Thread3, which is derived from Thread. The super() inside Thread3 invokes the parent Thread constructor e.g., public Thread(String tName).Here, tName specifies the name of the thread.

Example2: Creating multiple threads and using Thread class having isAlive() and join() method:

It is a program to ensure that the main thread is the last to stop.

class NewThread extends Thread{
 String name;// name of the thread.
 Thread t;
 NewThread(String threadname){
 name=threadname; 
 System.out.println("new thread:"+name);
 }
 //This is the entry point for the threads.
 public void run() 
 { 
 try
 {
 for(int i=3;i>0;i--)
 { 
 System.out.println(name+":"+i);
 Thread.sleep(1000);
 }
 }catch(InterruptedException e)
 {  
 System.out.println(name+"interrupted");
 }
 System.out.println(name+"exiting");
 }  
 } 
 public class Multithread { 
 public static void main(String args[]) 
 { 
 NewThread ob1= new NewThread("one");//start threads 
 NewThread ob2= new NewThread("Two");
 NewThread ob3=  new NewThread("Three");
 ob1.start();
 ob2.start(); 
 ob3.start();
 System.out.println("Thread one is alive:"+ob1.isAlive());
 System.out.println("Thread two is alive:"+ob2.isAlive());
 System.out.println("Thread three is alive:"+ob3.isAlive());
 System.out.println("Main thread exiting");
  //wait for threads to finish.  
  try 
 {//wait for the threads to finish.
 System.out.println("waiting for threads to finish");
 ob1.join();
  ob2.join();
  ob3.join(); 
 }catch(InterruptedException e) {
 System.out.println("Main thread Interrupted");
 }
 System.out.println("Thread one is alive"+ob1.isAlive());
 System.out.println("Thread two is alive"+ ob2.isAlive());
 System.out.println("thread three is alive"+ob3.isAlive());
 System.out.println("main thread exiting.");
 } 
 } 

Output:

Java Thread Creation3

Explanation:

If we want the main thread to finish last. The program is accomplished by calling sleep() within main(), but how can one thread know when another thread has ended its execution. We can call isAlive() on the thread to determine whether a thread has finished or not. If the thread upon which the isAlive() method is called is still running  it returns true. It returns false if the thread is not running.

The join() method causes to waits the other thread until the thread on which it is called terminates.

Difference between the Thread class and Runnable interface

Following are some key differences between Thread class and Runnable interface:

1. There is an additional method that has to override in the class, i.e., they consume excess or indirect memory, computation time, or other resources.

2. In Java, we can only extend one class, and therefore if we extend Thread class, then we will not be able to extend any other class. That is why we should implement the Runnable interface to create a thread.

3. Runnable makes the code more flexible as, if we are extending a thread, then our code will only be in a thread whereas, in case of runnable, one can pass it in various executor services, or pass it to the single-threaded environment.

4. Maintenance of the code is easy if we implement the Runnable interface.



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