Multithreading in Java: A Quick Guide**
## **What is Multithreading?**
Multithreading is the concurrent execution of two or more threads within a single program. In Java, multithreading allows for better CPU utilization and improved application performance by enabling multiple tasks to run simultaneously.
### **Key Benefits**
- **Enhanced Performance:** Executes tasks in parallel, improving efficiency.
- **Responsiveness:** Keeps applications responsive by running background tasks.
- **Simplified Code:** Leads to clearer and more manageable code structures.
## **Thread Lifecycle**
A thread in Java goes through several states during its lifecycle:
1. **New:** The thread is created but not yet started.
2. **Runnable:** The thread is ready to run and waiting for CPU time.
3. **Blocked:** The thread is waiting for a monitor lock (synchronization).
4. **Waiting:** The thread is waiting for another thread to perform a particular action (e.g., join, notify).
5. **Timed Waiting:** The thread is waiting for a specified period.
6. **Terminated:** The thread has completed execution.
## **Creating Threads**
Threads in Java can be created in two main ways:
1. **By Extending `Thread` Class:**
```java
class MyThread extends Thread {public void run() {System.out.println("Thread is running");}}MyThread thread = new MyThread();thread.start(); // Starts the thread
```
2. **By Implementing `Runnable` Interface:**
```java
class MyRunnable implements Runnable {public void run() {System.out.println("Thread is running");}}Thread thread = new Thread(new MyRunnable());thread.start(); // Starts the thread
```
## **Thread Methods**
Commonly used methods in the `Thread` class:
- `start()`: Starts the thread and invokes the `run()` method.
- `run()`: Contains the code to be executed by the thread.
- `sleep(long millis)`: Causes the thread to sleep for a specified duration.
- `join()`: Waits for the thread to die.
- `interrupt()`: Interrupts a thread.
## **Thread Priority**
Java threads have priorities that help the scheduler determine the order of execution. Priorities range from `Thread.MIN_PRIORITY` (1) to `Thread.MAX_PRIORITY` (10). The default priority is `Thread.NORM_PRIORITY` (5).
```java
Thread thread = new Thread(new MyRunnable());thread.setPriority(Thread.MAX_PRIORITY);
```
## **Thread Synchronization**
To prevent thread interference when multiple threads access shared resources, synchronization is used. This ensures that only one thread can access a resource at a time.
### **Synchronized Methods:**
```java
synchronized void myMethod() {
// synchronized code
}
```
### **Synchronized Blocks:**
```java
void myMethod() {synchronized(this) {// synchronized code}}
```
## **Inter-Thread Communication**
Java provides methods to allow threads to communicate with each other:
- **wait()**: Causes the current thread to wait until another thread calls `notify()` or `notifyAll()`.
- **notify()**: Wakes up a single thread that is waiting on the object’s monitor.
- **notifyAll()**: Wakes up all the threads that are waiting on the object’s monitor.
### **Example:**
```java
class SharedResource {synchronized void produce() {// produce somethingnotify(); // Notify waiting threads}synchronized void consume() {wait(); // Wait for producer// consume something}}
```
## **Conclusion**
Multithreading in Java is a powerful feature that enhances application performance and responsiveness. Understanding the thread lifecycle, creation methods, synchronization, and inter-thread communication is crucial for effectively leveraging multithreading in your Java applications. With this knowledge, you can build efficient and scalable programs that take full advantage of modern multi-core processors.
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