Java執行緒生命週期的終止與復位

public enum State {
    /**
     * 尚未啟動的執行緒的執行緒狀態 （沒有start）
     */
    NEW,

    /**
     * 可執行執行緒的執行緒狀態，是可以執行的執行緒狀態（並不是在執行）
     * 這個狀態在Java虛擬機器器中進行，但它可能等待來自作業系統的其他資源，比如CPU。
     * 內部包含了兩個狀態 【RUNNING】,【READY】這兩個狀態是可以互相流轉的
     * 呼叫了start後執行緒就處於 READY 狀態 ，等待作業系統分配CPU時間片，分配後進入 RUNNING 狀態。
     * 當呼叫 yield() 方法後，只是謙讓的允許當前執行緒讓出 CPU ，但是不一定讓，由作業系統決定，如果讓      * 了當前執行緒就會進入 READY 狀態，等待系統分配CPU時間片再次進入 RUNNING 狀態。
     */
    RUNNABLE,

    /**
     * 阻塞狀態。
     * 執行緒阻塞，等待監視器鎖的狀態，獲取監視器鎖後會進入 RUNNABLE  狀態
     * 當發生執行緒鎖競爭狀態下，沒有獲取到鎖的執行緒會被掛起進入阻塞狀態，比如synchronized鎖。
     */
    BLOCKED,

    /**
     * 等待執行緒的執行緒狀態
     * 執行緒呼叫以下方法會處於等待狀態：Object.wait()不超時、Thread.join()不超時等方法
     * 一個處於等待狀態的執行緒正在等待另一個執行緒執行特定動作，例如：
     * 一個執行緒呼叫了Object.wait()方法在一個物件上正在等待另一個執行緒呼叫Object.nofify()或者
     * Object.nofifyAll()方法開啟那個物件
     * 一個呼叫了Thread.join()方法的執行緒正在等待指定執行緒終止
     */
    WAITING,

    /**
     * 具有指定等待時間的等待執行緒的執行緒狀態，呼叫一下方法會處於這個狀態： Object.wait() 超時、          * Thread.join()超時 Thread.sleep(long) 等方法 
     */
    TIMED_WAITING,

    /**
     * 已終止執行緒的執行緒狀態
     * 執行緒執行完畢或者發生異常終止執行
     */
    TERMINATED;
}

public class ThreadStatusDemo {
    public static void main(String[] args) throws InterruptedException {
        // 測試 NEW RUNNABLE TERMINATED
        Thread terminated_thread = new Thread(() -> {
            long start = System.currentTimeMillis();
            // 執行三秒 ,列印TERMINATED_THREAD執行緒runnable狀態
            while (System.currentTimeMillis()-start<3000){}
        }, "TERMINATED_THREAD");
        // NEW
        Thread.State state = terminated_thread.getState();
        System.out.println(terminated_thread.getName()+" :state = " + state);

        terminated_thread.start();
        TimeUnit.SECONDS.sleep(1);
        // RUNNABLE
        Thread.State state1 = terminated_thread.getState();
        System.out.println(terminated_thread.getName()+"state1 = " + state1);

        TimeUnit.SECONDS.sleep(5);
        Thread.State state2 = terminated_thread.getState();
        // TERMINATED
        System.out.println(terminated_thread.getName()+"state2 = " + state2);

        // RUNNABLE
        new Thread(() -> {
            while (true) {

            }
        }, "Runnle_Thread").start();
        // TIMED_WAITING
        new Thread(() -> {
            while (true) {
                try {
                    TimeUnit.SECONDS.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "Time_Waiting_Thread").start();
        // WAITING
        new Thread(() -> {
            while (true) {
                synchronized (ThreadStatusDemo.class) {
                    try {
                        ThreadStatusDemo.class.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "Waiting_Thread").start();

        // 這兩個看誰先搶佔到cpu獲得鎖,另一個就blocked
        // timed_waiting
        new Thread(new BlockedDemo(), "Blocke01_Thread").start();
        // blocked
        new Thread(new BlockedDemo(), "Blocke02_Thread").start();
    }
    static class BlockedDemo extends Thread {
        @Override
        public void run() {
            synchronized (BlockedDemo.class) {
                while (true) {
                    try {
                        TimeUnit.SECONDS.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}

public synchronized void start() {
    . . .
    boolean started = false;
    try { 
        // 呼叫native方法
        start0();
        started = true;
    } finally {
        try {
            if (!started) {
                group.threadStartFailed(this);
            }
        } catch (Throwable ignore) {
            /* do nothing. If start0 threw a Throwable then
              it will be passed up the call stack */
        }
    }
}

JVM_ENTRY(void, JVM_StartThread(JNIEnv* env, jobject jthread))
  JVMWrapper("JVM_StartThread");
  JavaThread *native_thread = NULL;
  bool throw_illegal_thread_state = false;
  {
    MutexLocker mu(Threads_lock);

    if (java_lang_Thread::thread(JNIHandles::resolve_non_null(jthread)) != NULL) {
      throw_illegal_thread_state = true;
    } else {
      jlong size =
             java_lang_Thread::stackSize(JNIHandles::resolve_non_null(jthread));
      size_t sz = size > 0 ? (size_t) size : 0;
      // 先建立一個JavaThread
      native_thread = new JavaThread(&thread_entry, sz);
      if (native_thread->osthread() != NULL) {
        native_thread->prepare(jthread);
      }
    }
  }
  if (throw_illegal_thread_state) {
    THROW(vmSymbols::java_lang_IllegalThreadStateException());
  }
  assert(native_thread != NULL, "Starting null thread?");
  if (native_thread->osthread() == NULL) {
    delete native_thread;
    if (JvmtiExport::should_post_resource_exhausted()) {
      JvmtiExport::post_resource_exhausted(
        JVMTI_RESOURCE_EXHAUSTED_OOM_ERROR | JVMTI_RESOURCE_EXHAUSTED_THREADS,
        "unable to create new native thread");
    }
    THROW_MSG(vmSymbols::java_lang_OutOfMemoryError(),
              "unable to create new native thread");
  }
  // 然後啟動這個本地執行緒 thread.cpp
  Thread::start(native_thread);
JVM_END

JavaThread::JavaThread(ThreadFunction entry_point, size_t stack_sz) :
  Thread()
#if INCLUDE_ALL_GCS
  , _satb_mark_queue(&_satb_mark_queue_set),
  _dirty_card_queue(&_dirty_card_queue_set)
#endif // INCLUDE_ALL_GCS
{
  if (TraceThreadEvents) {
    tty->print_cr("creating thread %p", this);
  }
  initialize();
  _jni_attach_state = _not_attaching_via_jni;
  set_entry_point(entry_point);
  os::ThreadType thr_type = os::java_thread;
  thr_type = entry_point == &compiler_thread_entry ? os::compiler_thread :
                                                     os::java_thread
// 呼叫os(作業系統)建立個執行緒
  os::create_thread(this, thr_type, stack_sz);
  _safepoint_visible = false;
   . . .
}

// tips: 啟動執行緒的方法
void Thread::start(Thread* thread) {
  trace("start", thread);
  // Start is different from resume in that its safety is guaranteed by context or
  // being called from a Java method synchronized on the Thread object.
  if (!DisableStartThread) {
    if (thread->is_Java_thread()) {
      // Initialize the thread state to RUNNABLE before starting this thread.
      // Can not set it after the thread started because we do not know the
      // exact thread state at that time. It could be in MONITOR_WAIT or
      // in SLEEPING or some other state.
      // tips:啟動之後設定執行緒的狀態為 可執行狀態 RUNNABLE
      java_lang_Thread::set_thread_status(((JavaThread*)thread)->threadObj(),
                                          java_lang_Thread::RUNNABLE);
    }
    // 藉助作業系統啟動執行緒
    os::start_thread(thread);
  }
}

thread.cpp interrupt 借用作業系統。直接通過系統呼叫 interrupt
void Thread::interrupt(Thread* thread) {
  trace("interrupt", thread);
  debug_only(check_for_dangling_thread_pointer(thread);)
  // tips: 呼叫作業系統的interrupt方法
  os::interrupt(thread);
}