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Thread.java
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1740 lines (1595 loc) · 64.3 KB
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package java.lang;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.lang.ref.WeakReference;
import java.security.AccessController;
import java.security.AccessControlContext;
import java.security.PrivilegedAction;
import java.util.Map;
import java.util.HashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import sun.nio.ch.Interruptible;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;
import sun.security.util.SecurityConstants;
/**
* A <i>thread</i> is a thread of execution in a program. The Java
* Virtual Machine allows an application to have multiple threads of
* execution running concurrently.
* <p>
* Every thread has a priority. Threads with higher priority are
* executed in preference to threads with lower priority. Each thread
* may or may not also be marked as a daemon. When code running in
* some thread creates a new <code>Thread</code> object, the new
* thread has its priority initially set equal to the priority of the
* creating thread, and is a daemon thread if and only if the
* creating thread is a daemon.
* <p>
* When a Java Virtual Machine starts up, there is usually a single
* non-daemon thread (which typically calls the method named
* <code>main</code> of some designated class). The Java Virtual
* Machine continues to execute threads until either of the following
* occurs:
* <ul>
* <li>The <code>exit</code> method of class <code>Runtime</code> has been
* called and the security manager has permitted the exit operation
* to take place.
* <li>All threads that are not daemon threads have died, either by
* returning from the call to the <code>run</code> method or by
* throwing an exception that propagates beyond the <code>run</code>
* method.
* </ul>
* <p>
* There are two ways to create a new thread of execution. One is to
* declare a class to be a subclass of <code>Thread</code>. This
* subclass should override the <code>run</code> method of class
* <code>Thread</code>. An instance of the subclass can then be
* allocated and started. For example, a thread that computes primes
* larger than a stated value could be written as follows:
* <hr><blockquote><pre>
* class PrimeThread extends Thread {
* long minPrime;
* PrimeThread(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
* </pre></blockquote><hr>
* <p>
* The following code would then create a thread and start it running:
* <blockquote><pre>
* PrimeThread p = new PrimeThread(143);
* p.start();
* </pre></blockquote>
* <p>
* The other way to create a thread is to declare a class that
* implements the <code>Runnable</code> interface. That class then
* implements the <code>run</code> method. An instance of the class can
* then be allocated, passed as an argument when creating
* <code>Thread</code>, and started. The same example in this other
* style looks like the following:
* <hr><blockquote><pre>
* class PrimeRun implements Runnable {
* long minPrime;
* PrimeRun(long minPrime) {
* this.minPrime = minPrime;
* }
*
* public void run() {
* // compute primes larger than minPrime
* . . .
* }
* }
* </pre></blockquote><hr>
* <p>
* The following code would then create a thread and start it running:
* <blockquote><pre>
* PrimeRun p = new PrimeRun(143);
* new Thread(p).start();
* </pre></blockquote>
* <p>
* Every thread has a name for identification purposes. More than
* one thread may have the same name. If a name is not specified when
* a thread is created, a new name is generated for it.
* <p>
* Unless otherwise noted, passing a {@code null} argument to a constructor
* or method in this class will cause a {@link NullPointerException} to be
* thrown.
*
* @see Runnable
* @see Runtime#exit(int)
* @see #run()
* @see #stop()
*/
public class Thread implements Runnable {
/**
* 类加载的时候，调用本地的注册本地静态方法
*/
private static native void registerNatives();
static {
registerNatives();
}
/**
* 线程名称
*/
private volatile String name;
/**
* 优先级
*/
private int priority;
/**
* 是否是守护线程，true 是守护线程。如果是守护线程的话，是不能够阻止 JVM 的退出的，级别很低
*/
private boolean daemon = false;
/**
* JVM 状态
*/
private boolean stillborn = false;
/**
* 实际被执行的对象
*/
private Runnable target;
/**
* 该线程的线程组
*/
private ThreadGroup group;
/**
* 该线程的上下文类加载器
*/
private ClassLoader contextClassLoader;
/* The inherited AccessControlContext of this thread */
private AccessControlContext inheritedAccessControlContext;
/**
* 给线程自动生成名称所用
*/
private static int threadInitNumber;
/**
* 同一时刻只会有一个线程修改 threadInitNumber 的值，线程安全
*
* @return
*/
private static synchronized int nextThreadNum() {
return threadInitNumber++;
}
/**
* ThreadLocal 的 ThreadLocalMap 是线程的一个属性，所以在多线程环境下 threadLocals 是线程安全的
*/
ThreadLocal.ThreadLocalMap threadLocals = null;
/**
* 当创建子线程时，子线程可以得到父线程的 inheritableThreadLocals
*/
ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
/**
* 此线程请求的堆栈大小
*/
private long stackSize;
/*
* JVM-private state that persists after native thread termination.
*/
private long nativeParkEventPointer;
/**
* 线程 ID
*/
private long tid;
/**
* 用于生成线程 ID
*/
private static long threadSeqNumber;
/**
* 线程状态
*/
private volatile int threadStatus = 0;
/**
* 同一时刻只会有一个线程修改 threadSeqNumber 的值，线程安全
*
* @return
*/
private static synchronized long nextThreadID() {
return ++threadSeqNumber;
}
/**
* 此对象不为null时说明线程进入了park（阻塞）状态，参见 LockSupport
*
* @see java.util.concurrent.locks.LockSupport
*/
volatile Object parkBlocker;
/**
* 线程中断回调标记，设置此标记后，可在线程被中断时调用标记对象的回调方法
*/
private volatile Interruptible blocker;
/**
* 临时使用的锁，在设置/获取线程中断回调标记时使用
*/
private final Object blockerLock = new Object();
/**
* 为当前线程设置一个线程中断回调标记，以便在线程被中断时调用该标记的回调方法
*/
void blockedOn(Interruptible b) {
synchronized (blockerLock) {
blocker = b;
}
}
/**
* 最低优先级
*/
public final static int MIN_PRIORITY = 1;
/**
* 普通优先级，也是默认的
*/
public final static int NORM_PRIORITY = 5;
/**
* 最高优先级
*/
public final static int MAX_PRIORITY = 10;
/**
* 返回当前正在执行的线程对象的引用
*
* @return 当前正在执行的线程
*/
public static native Thread currentThread();
/**
* 当前线程做出让步，放弃当前 cpu，让线程重新选择 cpu，避免线程过度使用 cpu
* 让步不是不执行，也有可能重新选中自己
* 当前线程让出 cpu 时间片，重新抢占执行权
*/
public static native void yield();
/**
* 沉睡，锁不会释放，在 millis 毫秒之后会自己醒来
* 使线程进入 TIMED_WAITING 状态，millis毫秒后自己醒来（不释放锁）
*
* @param millis 睡眠时间
* @throws IllegalArgumentException 若 millis 为负数
* @throws InterruptedException if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public static native void sleep(long millis) throws InterruptedException;
/**
* 使线程进入TIMED_WAITING状态
* 至少等待millis毫秒，nanos是一个纳秒级的附加时间，用来微调millis参数（不释放锁）
*
* @param millis 睡眠时间
* @param nanos {@code 0-999999} 额外的纳秒睡眠时间
* @throws IllegalArgumentException if the value of {@code millis} is negative, or the value of
* {@code nanos} is not in the range {@code 0-999999}
* @throws InterruptedException if any thread has interrupted the current thread. The
* <i>interrupted status</i> of the current thread is
* cleared when this exception is thrown.
*/
public static void sleep(long millis, int nanos) throws InterruptedException {
if (millis < 0) {
throw new IllegalArgumentException("timeout value is negative");
}
if (nanos < 0 || nanos > 999999) {
throw new IllegalArgumentException(
"nanosecond timeout value out of range");
}
// 纳秒大于 0.5 毫秒，算一个毫秒
if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
millis++;
}
sleep(millis);
}
/**
* Initializes a Thread with the current AccessControlContext.
* @see #init(ThreadGroup,Runnable,String,long,AccessControlContext,boolean)
*/
private void init(ThreadGroup g, Runnable target, String name,
long stackSize) {
init(g, target, name, stackSize, null, true);
}
/**
* 初始化一个线程
*
* @param g 代表线程组，线程组可以对组内的线程进行批量的操作，比如批量的打断 interrupt
* @param target run（）方法被调用的对象，也就是我们要运行的对象
* @param name 新线程的名称
* @param stackSize 可以设置堆栈的大小
* @param acc the AccessControlContext to inherit, or
* AccessController.getContext() if null
* @param inheritThreadLocals if {@code true}, inherit initial values for
* inheritable thread-locals from the constructing thread
*/
private void init(ThreadGroup g, Runnable target, String name,
long stackSize, AccessControlContext acc,
boolean inheritThreadLocals) {
if (name == null) {
throw new NullPointerException("name cannot be null");
}
this.name = name;
// 当前线程作为父线程
Thread parent = currentThread();
// 如果安全管理器不为空，从安全管理器中拿线程组
// 否则继承父线程的线程组
SecurityManager security = System.getSecurityManager();
if (g == null) {
/* Determine if it's an applet or not */
/* If there is a security manager, ask the security manager
what to do. */
if (security != null) {
g = security.getThreadGroup();
}
/* If the security doesn't have a strong opinion of the matter
use the parent thread group. */
if (g == null) {
g = parent.getThreadGroup();
}
}
/* checkAccess regardless of whether or not threadgroup is
explicitly passed in. */
g.checkAccess();
/*
* Do we have the required permissions?
*/
if (security != null) {
if (isCCLOverridden(getClass())) {
security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
}
}
g.addUnstarted();
this.group = g;
// 子线程会继承父线程的守护属性
this.daemon = parent.isDaemon();
// 子线程继承父线程的优先级属性
this.priority = parent.getPriority();
if (security == null || isCCLOverridden(parent.getClass()))
this.contextClassLoader = parent.getContextClassLoader();
else
this.contextClassLoader = parent.contextClassLoader;
this.inheritedAccessControlContext =
acc != null ? acc : AccessController.getContext();
this.target = target;
setPriority(priority);
// 当父线程的 inheritableThreadLocals 的值不为空时
// 会把 inheritableThreadLocals 里面的值全部传递给子线程
if (inheritThreadLocals && parent.inheritableThreadLocals != null)
this.inheritableThreadLocals =
ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
/* Stash the specified stack size in case the VM cares */
this.stackSize = stackSize;
// 线程 id 自增
tid = nextThreadID();
}
/**
* Throws CloneNotSupportedException as a Thread can not be meaningfully
* cloned. Construct a new Thread instead.
*
* @throws CloneNotSupportedException
* always
*/
@Override
protected Object clone() throws CloneNotSupportedException {
throw new CloneNotSupportedException();
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, null, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*/
public Thread() {
init(null, null, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, gname)}, where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this classes {@code run} method does
* nothing.
*/
// 名称的初始化
public Thread(Runnable target) {
init(null, target, "Thread-" + nextThreadNum(), 0);
}
/**
* Creates a new Thread that inherits the given AccessControlContext.
* This is not a public constructor.
*/
Thread(Runnable target, AccessControlContext acc) {
init(null, target, "Thread-" + nextThreadNum(), 0, acc, false);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (group, target, gname)} ,where {@code gname} is a newly generated
* name. Automatically generated names are of the form
* {@code "Thread-"+}<i>n</i>, where <i>n</i> is an integer.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*/
public Thread(ThreadGroup group, Runnable target) {
init(group, target, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, null, name)}.
*
* @param name
* the name of the new thread
*/
public Thread(String name) {
init(null, null, name, 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (group, null, name)}.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param name
* the name of the new thread
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*/
public Thread(ThreadGroup group, String name) {
init(group, null, name, 0);
}
/**
* Allocates a new {@code Thread} object. This constructor has the same
* effect as {@linkplain #Thread(ThreadGroup,Runnable,String) Thread}
* {@code (null, target, name)}.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*/
public Thread(Runnable target, String name) {
init(null, target, name, 0);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* and belongs to the thread group referred to by {@code group}.
*
* <p>If there is a security manager, its
* {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
* method is invoked with the ThreadGroup as its argument.
*
* <p>In addition, its {@code checkPermission} method is invoked with
* the {@code RuntimePermission("enableContextClassLoaderOverride")}
* permission when invoked directly or indirectly by the constructor
* of a subclass which overrides the {@code getContextClassLoader}
* or {@code setContextClassLoader} methods.
*
* <p>The priority of the newly created thread is set equal to the
* priority of the thread creating it, that is, the currently running
* thread. The method {@linkplain #setPriority setPriority} may be
* used to change the priority to a new value.
*
* <p>The newly created thread is initially marked as being a daemon
* thread if and only if the thread creating it is currently marked
* as a daemon thread. The method {@linkplain #setDaemon setDaemon}
* may be used to change whether or not a thread is a daemon.
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group or cannot override the context class loader methods.
*/
public Thread(ThreadGroup group, Runnable target, String name) {
init(group, target, name, 0);
}
/**
* Allocates a new {@code Thread} object so that it has {@code target}
* as its run object, has the specified {@code name} as its name,
* and belongs to the thread group referred to by {@code group}, and has
* the specified <i>stack size</i>.
*
* <p>This constructor is identical to {@link
* #Thread(ThreadGroup,Runnable,String)} with the exception of the fact
* that it allows the thread stack size to be specified. The stack size
* is the approximate number of bytes of address space that the virtual
* machine is to allocate for this thread's stack. <b>The effect of the
* {@code stackSize} parameter, if any, is highly platform dependent.</b>
*
* <p>On some platforms, specifying a higher value for the
* {@code stackSize} parameter may allow a thread to achieve greater
* recursion depth before throwing a {@link StackOverflowError}.
* Similarly, specifying a lower value may allow a greater number of
* threads to exist concurrently without throwing an {@link
* OutOfMemoryError} (or other internal error). The details of
* the relationship between the value of the <tt>stackSize</tt> parameter
* and the maximum recursion depth and concurrency level are
* platform-dependent. <b>On some platforms, the value of the
* {@code stackSize} parameter may have no effect whatsoever.</b>
*
* <p>The virtual machine is free to treat the {@code stackSize}
* parameter as a suggestion. If the specified value is unreasonably low
* for the platform, the virtual machine may instead use some
* platform-specific minimum value; if the specified value is unreasonably
* high, the virtual machine may instead use some platform-specific
* maximum. Likewise, the virtual machine is free to round the specified
* value up or down as it sees fit (or to ignore it completely).
*
* <p>Specifying a value of zero for the {@code stackSize} parameter will
* cause this constructor to behave exactly like the
* {@code Thread(ThreadGroup, Runnable, String)} constructor.
*
* <p><i>Due to the platform-dependent nature of the behavior of this
* constructor, extreme care should be exercised in its use.
* The thread stack size necessary to perform a given computation will
* likely vary from one JRE implementation to another. In light of this
* variation, careful tuning of the stack size parameter may be required,
* and the tuning may need to be repeated for each JRE implementation on
* which an application is to run.</i>
*
* <p>Implementation note: Java platform implementers are encouraged to
* document their implementation's behavior with respect to the
* {@code stackSize} parameter.
*
*
* @param group
* the thread group. If {@code null} and there is a security
* manager, the group is determined by {@linkplain
* SecurityManager#getThreadGroup SecurityManager.getThreadGroup()}.
* If there is not a security manager or {@code
* SecurityManager.getThreadGroup()} returns {@code null}, the group
* is set to the current thread's thread group.
*
* @param target
* the object whose {@code run} method is invoked when this thread
* is started. If {@code null}, this thread's run method is invoked.
*
* @param name
* the name of the new thread
*
* @param stackSize
* the desired stack size for the new thread, or zero to indicate
* that this parameter is to be ignored.
*
* @throws SecurityException
* if the current thread cannot create a thread in the specified
* thread group
*
* @since 1.4
*/
public Thread(ThreadGroup group, Runnable target, String name,
long stackSize) {
init(group, target, name, stackSize);
}
/**
* 该方法可以创建一个新的线程出来，返回的仍然是主线程
* 启动线程，线程状态从 NEW 进入 RUNNABLE
*
* @throws IllegalThreadStateException 若线程已经启动
* @see #run()
* @see #stop()
*/
public synchronized void start() {
// 如果没有初始化，抛异常
if (threadStatus != 0)
throw new IllegalThreadStateException();
// 将当前线程加入到所在的线程组，记录为活跃线程
group.add(this);
// started 是个标识符，我们在初始化一些东西的时候，经常这么写
boolean started = false;
try {
// 这里会创建一个新的线程，执行完成之后，新的线程已经在运行了，既 target 的内容已经在运行了
start0();
// 这里执行的还是主线程
started = true;
} finally {
try {
// 如果失败，把线程从线程组中删除
if (!started) {
group.threadStartFailed(this);
}
// 这里的 catch 捕捉也是值得我们学习的，我们在工作中 catch 时也应该多用 Throwable，少用 Exception
// 比如对于异步线程抛出来的异常，Exception 是捕捉不住的，Throwable 却可以
} catch (Throwable ignore) {
/* do nothing. If start0 threw a Throwable then
it will be passed up the call stack */
}
}
}
/**
* 开启新线程使用的是 native 方法
*/
private native void start0();
/**
* 简单的运行，不会新起线程
*
* @see #start()
* @see #stop()
* @see #Thread(ThreadGroup, Runnable, String)
*/
@Override
public void run() {
if (target != null) {
target.run();
}
}
/**
* This method is called by the system to give a Thread
* a chance to clean up before it actually exits.
*/
private void exit() {
if (group != null) {
group.threadTerminated(this);
group = null;
}
/* Aggressively null out all reference fields: see bug 4006245 */
target = null;
/* Speed the release of some of these resources */
threadLocals = null;
inheritableThreadLocals = null;
inheritedAccessControlContext = null;
blocker = null;
uncaughtExceptionHandler = null;
}
/**
* Forces the thread to stop executing.
* <p>
* If there is a security manager installed, its <code>checkAccess</code>
* method is called with <code>this</code>
* as its argument. This may result in a
* <code>SecurityException</code> being raised (in the current thread).
* <p>
* If this thread is different from the current thread (that is, the current
* thread is trying to stop a thread other than itself), the
* security manager's <code>checkPermission</code> method (with a
* <code>RuntimePermission("stopThread")</code> argument) is called in
* addition.
* Again, this may result in throwing a
* <code>SecurityException</code> (in the current thread).
* <p>
* The thread represented by this thread is forced to stop whatever
* it is doing abnormally and to throw a newly created
* <code>ThreadDeath</code> object as an exception.
* <p>
* It is permitted to stop a thread that has not yet been started.
* If the thread is eventually started, it immediately terminates.
* <p>
* An application should not normally try to catch
* <code>ThreadDeath</code> unless it must do some extraordinary
* cleanup operation (note that the throwing of
* <code>ThreadDeath</code> causes <code>finally</code> clauses of
* <code>try</code> statements to be executed before the thread
* officially dies). If a <code>catch</code> clause catches a
* <code>ThreadDeath</code> object, it is important to rethrow the
* object so that the thread actually dies.
* <p>
* The top-level error handler that reacts to otherwise uncaught
* exceptions does not print out a message or otherwise notify the
* application if the uncaught exception is an instance of
* <code>ThreadDeath</code>.
*
* @exception SecurityException if the current thread cannot
* modify this thread.
* @see #interrupt()
* @see #checkAccess()
* @see #run()
* @see #start()
* @see ThreadDeath
* @see ThreadGroup#uncaughtException(Thread,Throwable)
* @see SecurityManager#checkAccess(Thread)
* @see SecurityManager#checkPermission
* @deprecated This method is inherently unsafe. Stopping a thread with
* Thread.stop causes it to unlock all of the monitors that it
* has locked (as a natural consequence of the unchecked
* <code>ThreadDeath</code> exception propagating up the stack). If
* any of the objects previously protected by these monitors were in
* an inconsistent state, the damaged objects become visible to
* other threads, potentially resulting in arbitrary behavior. Many
* uses of <code>stop</code> should be replaced by code that simply
* modifies some variable to indicate that the target thread should
* stop running. The target thread should check this variable
* regularly, and return from its run method in an orderly fashion
* if the variable indicates that it is to stop running. If the
* target thread waits for long periods (on a condition variable,
* for example), the <code>interrupt</code> method should be used to
* interrupt the wait.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@Deprecated
public final void stop() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
checkAccess();
if (this != Thread.currentThread()) {
security.checkPermission(SecurityConstants.STOP_THREAD_PERMISSION);
}
}
// A zero status value corresponds to "NEW", it can't change to
// not-NEW because we hold the lock.
if (threadStatus != 0) {
resume(); // Wake up thread if it was suspended; no-op otherwise
}
// The VM can handle all thread states
stop0(new ThreadDeath());
}
/**
* Throws {@code UnsupportedOperationException}.
*
* @param obj ignored
*
* @deprecated This method was originally designed to force a thread to stop
* and throw a given {@code Throwable} as an exception. It was
* inherently unsafe (see {@link #stop()} for details), and furthermore
* could be used to generate exceptions that the target thread was
* not prepared to handle.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@Deprecated
public final synchronized void stop(Throwable obj) {
throw new UnsupportedOperationException();
}
/**
* 中断线程（只是给线程预设一个标记，不是立即让线程停下来）
*
* @throws SecurityException 若当前线程无法修改
*/
public void interrupt() {
// 如果由别的线程对当前线程发起中断
if (this != Thread.currentThread())
checkAccess();
synchronized (blockerLock) {
Interruptible b = blocker;
// 如果存在线程中断回调标记
if (b != null) {
// 设置中断标记
interrupt0();
b.interrupt(this);
return;
}
}
interrupt0();
}
/**
* Tests whether the current thread has been interrupted. The
* <i>interrupted status</i> of the thread is cleared by this method. In
* other words, if this method were to be called twice in succession, the
* second call would return false (unless the current thread were
* interrupted again, after the first call had cleared its interrupted
* status and before the second call had examined it).
*
* <p>A thread interruption ignored because a thread was not alive
* at the time of the interrupt will be reflected by this method
* returning false.
*
* @return <code>true</code> if the current thread has been interrupted;
* <code>false</code> otherwise.
* @see #isInterrupted()
* @revised 6.0
*/
public static boolean interrupted() {
return currentThread().isInterrupted(true);
}
/**
* Tests whether this thread has been interrupted. The <i>interrupted
* status</i> of the thread is unaffected by this method.
*
* <p>A thread interruption ignored because a thread was not alive
* at the time of the interrupt will be reflected by this method
* returning false.
*
* @return <code>true</code> if this thread has been interrupted;
* <code>false</code> otherwise.
* @see #interrupted()
* @revised 6.0
*/
public boolean isInterrupted() {
return isInterrupted(false);
}
/**
* Tests if some Thread has been interrupted. The interrupted state
* is reset or not based on the value of ClearInterrupted that is
* passed.
*/
private native boolean isInterrupted(boolean ClearInterrupted);
/**
* Throws {@link NoSuchMethodError}.
*
* @deprecated This method was originally designed to destroy this
* thread without any cleanup. Any monitors it held would have
* remained locked. However, the method was never implemented.
* If if were to be implemented, it would be deadlock-prone in
* much the manner of {@link #suspend}. If the target thread held
* a lock protecting a critical system resource when it was
* destroyed, no thread could ever access this resource again.
* If another thread ever attempted to lock this resource, deadlock
* would result. Such deadlocks typically manifest themselves as
* "frozen" processes. For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">
* Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
* @throws NoSuchMethodError always
*/
@Deprecated
public void destroy() {
throw new NoSuchMethodError();
}
/**
* 判断当前线程是否仍然存活（没有到达 TERMINATED 状态）
*
* @return 若存活返回 true
*/
public final native boolean isAlive();
/**
* Suspends this thread.
* <p>
* First, the <code>checkAccess</code> method of this thread is called
* with no arguments. This may result in throwing a
* <code>SecurityException </code>(in the current thread).
* <p>
* If the thread is alive, it is suspended and makes no further
* progress unless and until it is resumed.
*
* @exception SecurityException if the current thread cannot modify
* this thread.
* @see #checkAccess
* @deprecated This method has been deprecated, as it is
* inherently deadlock-prone. If the target thread holds a lock on the
* monitor protecting a critical system resource when it is suspended, no
* thread can access this resource until the target thread is resumed. If
* the thread that would resume the target thread attempts to lock this
* monitor prior to calling <code>resume</code>, deadlock results. Such
* deadlocks typically manifest themselves as "frozen" processes.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@Deprecated
public final void suspend() {
checkAccess();
suspend0();
}
/**
* Resumes a suspended thread.
* <p>
* First, the <code>checkAccess</code> method of this thread is called
* with no arguments. This may result in throwing a
* <code>SecurityException</code> (in the current thread).
* <p>
* If the thread is alive but suspended, it is resumed and is
* permitted to make progress in its execution.
*
* @exception SecurityException if the current thread cannot modify this
* thread.
* @see #checkAccess
* @see #suspend()
* @deprecated This method exists solely for use with {@link #suspend},
* which has been deprecated because it is deadlock-prone.
* For more information, see
* <a href="{@docRoot}/../technotes/guides/concurrency/threadPrimitiveDeprecation.html">Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?</a>.
*/
@Deprecated
public final void resume() {
checkAccess();
resume0();
}
/**
* 设置线程优先级
*
* @param newPriority priority to set this thread to
* @throws IllegalArgumentException 如果优先级不在 MIN_PRIORITY 到 MAX_PRIORITY 范围内
* @throws SecurityException 若不能修改当前线程
* @see #getPriority
* @see #checkAccess()