In Java, threads are objects and can be created in two ways:

1. by extending the class Thread

2. by implementing the interface Runnable

In the first approach, a user-specified thread class is created by extending the class Thread and overriding its run () method. In the second approach, a thread is created by implementing the Runnable interface and overriding its run () method. In both approaches the run () method has to be overridden. Usually, the code that is to be executed by a thread is written in its run () method. The thread terminates when its run () method returns. [Read more…] about Creating Threads in Java

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Multithreading replaces event loop programming by dividing the tasks into discrete and logical units. Threads also helps in avoiding polling. Polling is usually implemented by a loop that is used to check some condition repeatedly. Once the condition is true, appropriate action is taken, this results in wastage of CPU time. Suppose that the producer has to wait until the consumer is finished before it generates more data. In a polling system, the consumer would waste many CPU cycles while it waits for the producer to produce. Once the producer has finished, it would start polling, wasting more CPU cycles waiting for the consumer to finish, and so on. [Read more…] about Interthread Communication in Java Example

Since multiple threads run independently without any communication between them, some problems may arise because of this asynchronous behavior of threads. Sometimes, we need an operation to be performed by only one thread at a time. Performing the same task by two threads simultaneously may lead to inconsistent results. So to ensure that two thread don’t execute the conflicting operations together and to initiate communication among thread, a process called synchronization is used. [Read more…] about Synchronization in Java Example

Thread priorities are used by the thread scheduler to decide when each thread should be allowed to run. Higher priority threads get more CPU time than lower priority threads. A higher-priority thread can also preempt a lower-priority one. For instance, when a lower-priority thread is running and a higher-priority thread resumes (from sleeping or waiting on I/O, for example), it will preempt the lower priority thread. [Read more…] about Thread Priorities Example in Java

[Read more…] about Four Threads in Java Example

[Read more…] about isAlive() and Join() Example in Java By Inheriting Thread Class

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To determine whether a thread has finished. we can call isAlive() on the thread. This method is defined by Thread and its syntax is :

final boolean isAlive()

This method returns true if the thread upon which it is called is still running otherwise it returns false.

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[Read more…] about Two Threads in Java by Implementing Runnable Interface

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[Read more…] about Multiple Threads in Java by Implementing Runnable Interface

We first make a class MultipleThreads which extends Thread class and then we create an instance of that class t1 and pass the string “Child Thread” as parameter to it which assigns the name of the thread as Child Thread and also displays the information of the child thread on the screen. After that the start() method is invoked on that object which initiates the run() method. Before executing run() method of MultipleThreads, control returns to main(). In main() method, the for loop is executed which is supposed to print Mainthread : 1 [Read more…] about Multiple Threads in Java Example

Another method to create a thread is to create a class that implements the Runnable interface. Runnable abstracts a unit of executable code. We can construct a thread on any object that implements Runnable. To implement Runnable, a class need only implement a single method called run(). [Read more…] about Implementing Runnable Interface in Java Example

One way to create a thread is to create a new class that extends Thread, and then to create an instance of that class. The extending class must override the run() method, which is the entry point for the new thread. It must also call start() to begin execution of the new thread. [Read more…] about Extending Thread Class in Java Example

In this Java Example, a reference to the current thread (the main thread) is obtained by calling currentThread(), and this reference is stored in a local variable t. Then, we display the information about the thread. After that, a loop counts from 0 to 10, pausing one second between each line. The pause is accomplished by the sleep() method. The argument to sleep() specifies the delay period in milliseconds. The sleep() method might throw an InterruptedException if some other thread interrupts the sleeping one. [Read more…] about currentThread() in Java Example

Java has two types of threads : user thread and daemon thread. [Read more…] about Daemon Threads in Java Examples

Every thread in Java has a priority that helps the thread scheduler to determine the order in which threads scheduled. The threads with higher priority will usually run before and more frequently than lower priority threads. By default, all the threads had the same priority, i.e., they regarded as being equally distinguished by the scheduler, when a thread created it inherits its priority from the thread that created it. However, you can explicitly set a thread’s priority at any time after its creation by calling its setPriority() method. This method accepts an argument of type int that defines the new priority of the thread. Its syntax is. [Read more…] about Thread Priority in Java Example

When a large number of threads are created, degrades the performance of your application. So Java provides a technique of thread pooling to solve this problem.

The thread pooling allows you to reuse a single thread repeatedly instead of creating a new thread for each task and allowing it to be destroyed when the task completes. It avoids the overhead associated with creating a new thread by maintaining a pool of available threads and retrieving one from the pool when necessary. [Read more…] about Thread Pools in Java Example

In order to apply locks explicitly, an instance of the Lock interface needs to be created which is defined in the java.util.concurrent. Locks package. Using the Lock interface is similar to using the synchronized keyword. The Lock interface provides lock () and unlock () methods to acquire and release the lock respectively. [Read more…] about Explicit Locks in Java Example

Method level synchronization prevents two threads from executing method on an object at the same time. A method can be synchronized by using the synchronized keyword as a modifier in the method declaration. Its syntax is a follows, [Read more…] about Method Level Synchronization in Java Example

final void join () – The isAlive () method occasionally useful as continuously checking the value returned by this method and then sleeping makes a very inefficient use of the CPU time. So a better alternative to wait for a thread to die is to use join () method of the Thread class. [Read more…] about Join() Method in Java Example

In order to make sure that the main thread finishes last, we introduced a long enough delay by calling the sleep () method within the main() method so that all other threads finish before the main thread. But this of course is hardly a satisfactory solution because if your estimate for the time delay is too short then other threads could finish after the main thread finishes. Therefore, the Thread class provide method isAli ve ()  to determine if a thread has ended . [Read more…] about isAlive() in Java Example

Another way to create a thread in Java is to define a class that implements the Runnable interface. The previous technique of creating threads by extending the Thread class does not work when you want a class that extends another class and can also run as a thread. It is because java supports only single inheritance, i.e., does not allow a class to extend more than one class. So in such a case implement the Runnable interface. The Runnable interface declares only one method run () that contains the code executed when the thread started. Therefore, if you define a class that implements the Runnable interface, then it must implement the run () method. [Read more…] about Creating Thread Using Runnable Interface in Java Example

In this Example, we shows how the constructors and methods of the Thread class are used. Here, we have created a subclass MyThread that extends Thread class. This class consists of a field which stores the time in milliseconds for which the thread will sleep. It also contains a parameterized constructor that contains two parameters str of String type and d of int type. This constructor calls the superclass constructor that sets the Thread’s name to the value passed in str and delay field is set to value passed in d. [Read more…] about Constructors and Methods of the Thread Class in Java with Example