Java Tutorial

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Java Loops

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Java Programs

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Java Sorting

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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

Multithreading Program in Java

Multithreading Program in Java: Before discussing multithreading, it is important to discuss threads. Threads are the most fundamental part of a process. A process can have one or more threads. The execution of one thread is independent of another thread. Thus, when some error/ exception is generated in one thread, it does not hamper the process of another thread. All threads of the same process share the same memory space. Multithreading is the process of handling more than one thread simultaneously. The multithreading program in Java demonstrates the usage/ implementation of multithreading in the programming world.

Purpose of Multithreading

Multithreading ensures the maximum utilization of the CPU time when a program is executed. If a program is required to complete more than one task, which is independent of each other, multithreading is required.

Different States of a Thread in Java

The different states of a Thread are:

  • New: A thread whose execution has not started comes in this stage.
  • Runnable: After the start() method is called, the thread is in the queue for processing and ready to run, i.e., the thread scheduler has not selected the thread to move it to the running state. In other words, threads in this stage are waiting for the CPU for execution.
  • Running: The thread scheduler has moved the thread from runnable to this stage, which means the thread gets the CPU, and its execution is started. Note that the Runnable and Running stages form the active state of a thread.
  • Blocked/ Waiting: A thread that is still alive but is not eligible to enter the active state. A thread may enter this stage if a high-priority thread intervenes.
  • Dead/ Terminated: A thread that can no longer be used in a program. Usually, a thread enters this stage when the thread has completed its task or is forcefully terminated.

The following figure depicts the states of a thread.

Multithreading Program in Java

Creating a Thread in Java

There are two ways to create thread in Java.

1) By inheriting the Thread class

2) By implementing the Runnable Interface

Let’s discuss each of these given ways.

By inheriting the Thread class

Thread class implements the Runnable interface. In the Runnable interface, there is a method called run() that is like the service method of the thread. We need to override it in our thread class. See the following example.

FileName: UserThreadExample.Java

 // A class that inherits the class Thread
class MyThread extends Thread
{
   String m;
   int x;
    // constructor of the class
    public MyThread(String m)
    {
        this.m = m;
        x = 5;
    }
    // implemeting run() from
    // the Runnable interface
    public void run()
    {
        for(int i = 1; i <= x; i++)
        {
            System.out.println(m);
        }
    }
}
public class UserThreadExample
{
    // driver method
    public static void main(String argvs[])
    {
        MyThread t1 = new MyThread("Hello");
        MyThread t2 = new MyThread("Hi");
        MyThread t3 = new MyThread("Bye");
        // invoking the method start()
        t1.start();
        t2.start();
        t3.start();
    }
} 

Output:

 Hello
Bye
Hi
Hi
Hi
Hi
Hi
Bye
Bye
Bye
Bye
Hello
Hello
Hello
Hello 

Explanation: In the above code, we have created three threads. When the start() method is invoked, the thread enters in the active state. The start() method internally calls the run() method. A thread can never invoke the start() method more than once. If happens the same, it throws java.lang.IllegalThreadStateException is thrown. First, we have executed the threads t1, then t2, and finally t3. However, it does not guarantee that thread t1 is executed first. It is the duty of the thread scheduler to decide which thread will be executed first. We observe that four “Hello” are printing after “Bye”. If we execute our code again, it might happen we get different output. This is because context switching between the threads is not controlled by us.

Note: Every Java program has one thread called the main thread. The main thread is responsible for the execution of the main/ driver method. Thus, in the above example, there are 4 threads are executing. 

By Implementation the Runnable Interface

FileName: UserThreadExample1.Java

 // A class that implements the interface Runnable
public class UserThreadExample1 implements Runnable
{
   public void run()
   {
      System.out.println("Inside the method run ...");
   }
   public static void main(String argvs[])
   {
      // Creating an object of the class UserThreadExample1
      UserThreadExample1 usrObj = new UserThreadExample1();
      // Creating a thread t1 using the object usrObj
      Thread t1 =new Thread(usrObj);
      // starting the thread by invoking the start() method.
      t1.start();
   }
} 

Output:

Inside the method run ...

Explanation: The Runnable interface contains only a method called run(). The object (usrObj) is of the class UserThreadExample1. The class UserThreadExample1 implements the interface Runnable. It does not contain the method start(). The start() method is present in the class Thread. Therefore, we have created a thread t1 using the object usrObj. Finally, using the thread t1, the method start() is invoked to being the execution of the thread.

Priorities of a Thread

The scheduling of a thread is determined with the help of its priorities by an operating system. The range of priorities varies between 1 – 10. The MIN_PRIORITY takes the constant value 1, and MAX_PRIORITY takes the constant value 10. NORM_PRIORITY, which takes the constant value 5, is the default priority of a thread in Java. A thread with a high priority value is more important as compared to a thread with a low priority value. Therefore, the processor time of the high priority thread is allocated first, whereas the allocation of processor time is done later for the low priority thread. Note that high/ low priority does not guarantee the order of execution of threads. The order of execution of threads is very much dependent on the platform.



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