What is a Constructor in Java? In Java, a constructor is a special type of method that is used to initialize objects. When you create an object of a class, the constructor is called automatically. Its main job is to set the initial values of the object’s properties or perform any setup that the object needs before it can be used. Why Do We Need Constructors? You need constructors because: Initialization : Constructors are responsible for initializing an object when it is created. Automatic Execution : A constructor is automatically called when an object is created, so you don’t have to manually initialize every property. Simplifying Object Creation : It simplifies object creation by providing default values or custom initialization. Where Do Constructors Fit in Java? Constructors fit within a class. They are used whenever a new object of that class is created, and they allow the object to be initialized. Constructors must have the same name as the class, and they don't have a re...
In Java, there are two primary ways to create threads:
1. Extending the `Thread` class: You can create a new class that extends the `Thread` class and override its `run()` method to define the code that the thread will execute.
2. Implementing the `Runnable` interface: You can create a class that implements the `Runnable` interface and provide the implementation for its `run()` method. Then, you can pass an instance of this class to a `Thread` object.
Let's see examples for both approaches:
1. Extending the `Thread` class:
class MyThread extends Thread {
public void run() {
// Code to be executed by the thread
for (int i = 0; i < 5; i++) {
System.out.println("Thread: " + i);
try {
Thread.sleep(1000); // Pause execution for 1 second
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class Main {
public static void main(String[] args) {
MyThread thread = new MyThread();
thread.start(); // Start the thread
}
}
2. Implementing the `Runnable` interface:
class MyRunnable implements Runnable {
public void run() {
// Code to be executed by the thread
for (int i = 0; i < 5; i++) {
System.out.println("Runnable: " + i);
try {
Thread.sleep(1000); // Pause execution for 1 second
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public class Main {
public static void main(String[] args) {
MyRunnable myRunnable = new MyRunnable();
Thread thread = new Thread(myRunnable);
thread.start(); // Start the thread
}
}
Both approaches will create a separate thread of execution, allowing the code within the `run()` method (defined in either the `Thread` subclass or the `Runnable` implementation) to run concurrently with the main program.
Remember to call the `start()` method on the `Thread` object to start the execution of the thread. Do not call the `run()` method directly, as it will execute in the same thread as the caller, not in a separate thread.
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