Analysis of Java thread state transitions and operation examples

Understanding the changes in Java thread status and its corresponding operations requires specific code examples

In Java multi-thread programming, thread status changes are very important. Understanding the state changes of threads and how to operate threads will help us better grasp the core concepts of multi-threaded programming.

Java's thread status can be divided into 6 types: New (New), Ready (Runnable), Running (Running), Blocked (Blocked), Waiting (Waiting) and Terminated (Terminated). Below we will introduce these states one by one and give corresponding code examples.

1. New state (New):
   In the new state, the thread object has been created, but its start() method has not been called yet. In this state, the thread does not occupy CPU resources.
   The following is a sample code to create a new thread:

Thread thread = new Thread();

2. Ready state (Runnable):
   In the ready state, the thread has called the start() method, waiting Allocation of resources for execution. When a thread obtains CPU resources, it enters the running state.
   The following is a sample code for a thread to enter the ready state:

Thread thread = new Thread(() -> {
    // 执行一些任务
});

thread.start();

3. Running state (Running):
   In the running state, the thread is executing tasks. Threads can actively give up CPU resources, or they can be preempted by other high-priority threads.
   The following is a sample code for a thread to enter the running state:

Thread thread = new Thread(() -> {
    // 执行一些任务
});

thread.start();

4. Blocked state (Blocked):
   In the blocked state, the thread is waiting for the release of a resource. When a certain condition is met, the thread will re-enter the ready state.
   The following is a sample code for a thread to enter the blocking state:

Object lock = new Object();

Thread thread1 = new Thread(() -> {
    synchronized (lock) {
        try {
            lock.wait();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
});

Thread thread2 = new Thread(() -> {
    synchronized (lock) {
        lock.notify();
    }
});

thread1.start();
thread2.start();

In the above code, the thread1 thread calls the lock.wait() method to enter the blocking state until the thread2 thread calls lock.notify () method wakes it up.

5. Waiting state (Waiting):
   In the waiting state, the thread is waiting for a certain condition to be satisfied. Unlike the blocking state, threads in the waiting state require other threads to wake up.
   The following is a sample code for a thread to enter the waiting state:

Object lock = new Object();

Thread thread1 = new Thread(() -> {
    synchronized (lock) {
        try {
            lock.wait();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
});

Thread thread2 = new Thread(() -> {
    synchronized (lock) {
        lock.notify();
    }
});

thread1.start();
thread2.start();

In the above code, the thread1 thread calls the lock.wait() method to enter the waiting state until the thread2 thread calls lock.notify () method wakes it up.

6. Terminated state (Terminated):
   In the terminated state, the thread has completed the task or terminated due to an exception. A thread in a terminated state cannot change back to another state.
   The following is a sample code for a thread to enter the terminated state:

Thread thread = new Thread(() -> {
    // 执行一些任务
});

thread.start();

// 等待线程执行完毕
thread.join();

In the above code, by calling the thread.join() method, the main thread will wait for the thread thread to complete the task. Keep running.

In summary, understanding the changes in Java thread status and corresponding operations is crucial for multi-threaded programming. Through code examples, we can more intuitively understand the characteristics of each thread state and how to perform state transition operations.

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