java多线程二、Thread类
前言
Thread用来对线程创建与管理的一个类，实现了Runnable接口。接下来我们将详细学习该类。
线程的状态
线程一共有6个状态，对应如下 State enum
public enum State {
/**
* 对应 new Thread(Runnable target) 但是还没有调用start()方法
*/
NEW,
/**
* 对应 new Thread(Runnable target).start() 后的状态
* 包括通常我们所说的 就绪 与 运行 状态
*/
RUNNABLE,
/**
* Thread state for a thread blocked waiting for a monitor lock.
* A thread in the blocked state is waiting for a monitor lock
* to enter a synchronized block/method or
* reenter a synchronized block/method after calling
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
*
* - {@link Object#wait() Object.wait} with no timeout
* - {@link #join() Thread.join} with no timeout
* - {@link LockSupport#park() LockSupport.park}
*
*
* A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called Object.wait()
* on an object is waiting for another thread to call
* Object.notify() or Object.notifyAll() on
* that object. A thread that has called Thread.join()
* is waiting for a specified thread to terminate.
*/
WAITING,
/**
* Thread state for a waiting thread with a specified waiting time.
* A thread is in the timed waiting state due to calling one of
* the following methods with a specified positive waiting time:
*
* - {@link #sleep Thread.sleep}
* - {@link Object#wait(long) Object.wait} with timeout
* - {@link #join(long) Thread.join} with timeout
* - {@link LockSupport#parkNanos LockSupport.parkNanos}
* - {@link LockSupport#parkUntil LockSupport.parkUntil}
*
*/
TIMED_WAITING,
/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}
Thread 类
部分不常用的变量与方法这里不列出来，如有需要自己看源码
/**
* A thread is a thread of execution in a program. The Java
* Virtual Machine allows an application to have multiple threads of
* execution running concurrently.
*
* 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 Thread 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.
*
* When a Java Virtual Machine starts up, there is usually a single
* non-daemon thread (which typically calls the method named
* main of some designated class). The Java Virtual
* Machine continues to execute threads until either of the following
* occurs:
*
* - The
exit method of class Runtime has been
* called and the security manager has permitted the exit operation
* to take place.
* - All threads that are not daemon threads have died, either by
* returning from the call to the
run method or by
* throwing an exception that propagates beyond the run
* method.
*
* 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.
*
*/
public class Thread implements Runnable {
private volatile String name;
private int priority;
/* Whether or not the thread is a daemon thread. */
private boolean daemon = false;
/* What will be run. */
private Runnable target;
/* The group of this thread */
private ThreadGroup group;
/*
* Thread ID
*/
private long tid;
/* For generating thread ID */
private static long threadSeqNumber;
private volatile int threadStatus = 0;
private static synchronized long nextThreadID() {
return ++threadSeqNumber;
}
/**
* The minimum priority that a thread can have.
*/
public final static int MIN_PRIORITY = 1;
/**
* The default priority that is assigned to a thread.
*/
public final static int NORM_PRIORITY = 5;
/**
* The maximum priority that a thread can have.
*/
public final static int MAX_PRIORITY = 10;
/**
* Returns a reference to the currently executing thread object.
*
* @return the currently executing thread.
*/
public static native Thread currentThread();
/**
* A hint to the scheduler that the current thread is willing to yield
* its current use of a processor. The scheduler is free to ignore this
* hint.
*
* Yield is a heuristic attempt to improve relative progression
* between threads that would otherwise over-utilise a CPU. Its use
* should be combined with detailed profiling and benchmarking to
* ensure that it actually has the desired effect.
*
*
It is rarely appropriate to use this method. It may be useful
* for debugging or testing purposes, where it may help to reproduce
* bugs due to race conditions. It may also be useful when designing
* concurrency control constructs such as the ones in the
* {@link java.util.concurrent.locks} package.
*/
public static native void yield();
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds, subject to
* the precision and accuracy of system timers and schedulers. The thread
* does not lose ownership of any monitors.
*
* @param millis
* the length of time to sleep in milliseconds
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public static native void sleep(long millis) throws InterruptedException;
/**
* Causes the currently executing thread to sleep (temporarily cease
* execution) for the specified number of milliseconds plus the specified
* number of nanoseconds, subject to the precision and accuracy of system
* timers and schedulers. The thread does not lose ownership of any
* monitors.
*
* @param millis
* the length of time to sleep in milliseconds
*
* @param nanos
* {@code 0-999999} additional nanoseconds to sleep
*
* @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
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public static void sleep(long millis, int nanos) throws InterruptedException {...}
/**
* 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-"+}n, where n 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-"+}n, where n 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.
*/
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-"+}n, where n 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}.
*
* If there is a security manager, its
* {@link SecurityManager#checkAccess(ThreadGroup) checkAccess}
* method is invoked with the ThreadGroup as its argument.
*
*
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.
*
*
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.
*
*
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 stack size.
*
* 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. The effect of the
* {@code stackSize} parameter, if any, is highly platform dependent.
*
*
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 stackSize parameter
* and the maximum recursion depth and concurrency level are
* platform-dependent. On some platforms, the value of the
* {@code stackSize} parameter may have no effect whatsoever.
*
*
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).
*
*
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.
*
*
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.
*
*
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);
}
/**
* Causes this thread to begin execution; the Java Virtual Machine
* calls the run method of this thread.
*
* The result is that two threads are running concurrently: the
* current thread (which returns from the call to the
* start method) and the other thread (which executes its
* run method).
*
* It is never legal to start a thread more than once.
* In particular, a thread may not be restarted once it has completed
* execution.
*
* @exception IllegalThreadStateException if the thread was already
* started.
* @see #run()
* @see #stop()
*/
public synchronized void start() {...}
/**
* If this thread was constructed using a separate
* Runnable run object, then that
* Runnable object's run method is called;
* otherwise, this method does nothing and returns.
*
* Subclasses of Thread should override this method.
*
* @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.
*
* If there is a security manager installed, its checkAccess
* method is called with this
* as its argument. This may result in a
* SecurityException being raised (in the current thread).
*
* 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 checkPermission method (with a
* RuntimePermission("stopThread") argument) is called in
* addition.
* Again, this may result in throwing a
* SecurityException (in the current thread).
*
* The thread represented by this thread is forced to stop whatever
* it is doing abnormally and to throw a newly created
* ThreadDeath object as an exception.
*
* It is permitted to stop a thread that has not yet been started.
* If the thread is eventually started, it immediately terminates.
*
* An application should not normally try to catch
* ThreadDeath unless it must do some extraordinary
* cleanup operation (note that the throwing of
* ThreadDeath causes finally clauses of
* try statements to be executed before the thread
* officially dies). If a catch clause catches a
* ThreadDeath object, it is important to rethrow the
* object so that the thread actually dies.
*
* 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
* ThreadDeath.
*
* @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
* ThreadDeath 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 stop 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 interrupt method should be used to
* interrupt the wait.
* For more information, see
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@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
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@Deprecated
public final synchronized void stop(Throwable obj) {
throw new UnsupportedOperationException();
}
/**
* Interrupts this thread.
*
* Unless the current thread is interrupting itself, which is
* always permitted, the {@link #checkAccess() checkAccess} method
* of this thread is invoked, which may cause a {@link
* SecurityException} to be thrown.
*
*
If this thread is blocked in an invocation of the {@link
* Object#wait() wait()}, {@link Object#wait(long) wait(long)}, or {@link
* Object#wait(long, int) wait(long, int)} methods of the {@link Object}
* class, or of the {@link #join()}, {@link #join(long)}, {@link
* #join(long, int)}, {@link #sleep(long)}, or {@link #sleep(long, int)},
* methods of this class, then its interrupt status will be cleared and it
* will receive an {@link InterruptedException}.
*
*
If this thread is blocked in an I/O operation upon an {@link
* java.nio.channels.InterruptibleChannel InterruptibleChannel}
* then the channel will be closed, the thread's interrupt
* status will be set, and the thread will receive a {@link
* java.nio.channels.ClosedByInterruptException}.
*
*
If this thread is blocked in a {@link java.nio.channels.Selector}
* then the thread's interrupt status will be set and it will return
* immediately from the selection operation, possibly with a non-zero
* value, just as if the selector's {@link
* java.nio.channels.Selector#wakeup wakeup} method were invoked.
*
*
If none of the previous conditions hold then this thread's interrupt
* status will be set.
*
* Interrupting a thread that is not alive need not have any effect.
*
* @throws SecurityException
* if the current thread cannot modify this thread
*
* @revised 6.0
* @spec JSR-51
*/
public void interrupt() {
if (this != Thread.currentThread())
checkAccess();
synchronized (blockerLock) {
Interruptible b = blocker;
if (b != null) {
interrupt0(); // Just to set the interrupt flag
b.interrupt(this);
return;
}
}
interrupt0();
}
/**
* Tests whether the current thread has been interrupted. The
* interrupted status 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).
*
* 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 true if the current thread has been interrupted;
* false otherwise.
* @see #isInterrupted()
* @revised 6.0
*/
public static boolean interrupted() {
return currentThread().isInterrupted(true);
}
/**
* Tests whether this thread has been interrupted. The interrupted
* status of the thread is unaffected by this method.
*
* 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 true if this thread has been interrupted;
* false 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
*
* Why are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
* @throws NoSuchMethodError always
*/
@Deprecated
public void destroy() {
throw new NoSuchMethodError();
}
/**
* Tests if this thread is alive. A thread is alive if it has
* been started and has not yet died.
*
* @return true if this thread is alive;
* false otherwise.
*/
public final native boolean isAlive();
/**
* Suspends this thread.
*
* First, the checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException (in the current thread).
*
* 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 resume, deadlock results. Such
* deadlocks typically manifest themselves as "frozen" processes.
* For more information, see
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@Deprecated
public final void suspend() {
checkAccess();
suspend0();
}
/**
* Resumes a suspended thread.
*
* First, the checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException (in the current thread).
*
* 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
* Why
* are Thread.stop, Thread.suspend and Thread.resume Deprecated?.
*/
@Deprecated
public final void resume() {
checkAccess();
resume0();
}
/**
* Changes the priority of this thread.
*
* First the checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException.
*
* Otherwise, the priority of this thread is set to the smaller of
* the specified newPriority and the maximum permitted
* priority of the thread's thread group.
*
* @param newPriority priority to set this thread to
* @exception IllegalArgumentException If the priority is not in the
* range MIN_PRIORITY to
* MAX_PRIORITY.
* @exception SecurityException if the current thread cannot modify
* this thread.
* @see #getPriority
* @see #checkAccess()
* @see #getThreadGroup()
* @see #MAX_PRIORITY
* @see #MIN_PRIORITY
* @see ThreadGroup#getMaxPriority()
*/
public final void setPriority(int newPriority) {
ThreadGroup g;
checkAccess();
if (newPriority > MAX_PRIORITY || newPriority < MIN_PRIORITY) {
throw new IllegalArgumentException();
}
if((g = getThreadGroup()) != null) {
if (newPriority > g.getMaxPriority()) {
newPriority = g.getMaxPriority();
}
setPriority0(priority = newPriority);
}
}
/**
* Returns this thread's priority.
*
* @return this thread's priority.
* @see #setPriority
*/
public final int getPriority() {
return priority;
}
/**
* Changes the name of this thread to be equal to the argument
* name.
*
* First the checkAccess method of this thread is called
* with no arguments. This may result in throwing a
* SecurityException.
*
* @param name the new name for this thread.
* @exception SecurityException if the current thread cannot modify this
* thread.
* @see #getName
* @see #checkAccess()
*/
public final synchronized void setName(String name) {
checkAccess();
if (name == null) {
throw new NullPointerException("name cannot be null");
}
this.name = name;
if (threadStatus != 0) {
setNativeName(name);
}
}
/**
* Returns this thread's name.
*
* @return this thread's name.
* @see #setName(String)
*/
public final String getName() {
return name;
}
/**
* Counts the number of stack frames in this thread. The thread must
* be suspended.
*
* @return the number of stack frames in this thread.
* @exception IllegalThreadStateException if this thread is not
* suspended.
* @deprecated The definition of this call depends on {@link #suspend},
* which is deprecated. Further, the results of this call
* were never well-defined.
*/
@Deprecated
public native int countStackFrames();
/**
* Waits at most {@code millis} milliseconds for this thread to
* die. A timeout of {@code 0} means to wait forever.
*
* This implementation uses a loop of {@code this.wait} calls
* conditioned on {@code this.isAlive}. As a thread terminates the
* {@code this.notifyAll} method is invoked. It is recommended that
* applications not use {@code wait}, {@code notify}, or
* {@code notifyAll} on {@code Thread} instances.
*
* @param millis
* the time to wait in milliseconds
*
* @throws IllegalArgumentException
* if the value of {@code millis} is negative
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public final synchronized void join(long millis)
throws InterruptedException {
long base = System.currentTimeMillis();
long now = 0;
if (millis < 0) {
throw new IllegalArgumentException("timeout value is negative");
}
if (millis == 0) {
while (isAlive()) {
wait(0);
}
} else {
while (isAlive()) {
long delay = millis - now;
if (delay <= 0) {
break;
}
wait(delay);
now = System.currentTimeMillis() - base;
}
}
}
/**
* Waits at most {@code millis} milliseconds plus
* {@code nanos} nanoseconds for this thread to die.
*
* This implementation uses a loop of {@code this.wait} calls
* conditioned on {@code this.isAlive}. As a thread terminates the
* {@code this.notifyAll} method is invoked. It is recommended that
* applications not use {@code wait}, {@code notify}, or
* {@code notifyAll} on {@code Thread} instances.
*
* @param millis
* the time to wait in milliseconds
*
* @param nanos
* {@code 0-999999} additional nanoseconds to wait
*
* @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
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public final synchronized void join(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");
}
if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
millis++;
}
join(millis);
}
/**
* Waits for this thread to die.
*
* An invocation of this method behaves in exactly the same
* way as the invocation
*
*
* {@linkplain #join(long) join}{@code (0)}
*
*
* @throws InterruptedException
* if any thread has interrupted the current thread. The
* interrupted status of the current thread is
* cleared when this exception is thrown.
*/
public final void join() throws InterruptedException {
join(0);
}
/**
* Prints a stack trace of the current thread to the standard error stream.
* This method is used only for debugging.
*
* @see Throwable#printStackTrace()
*/
public static void dumpStack() {
new Exception("Stack trace").printStackTrace();
}
/**
* Marks this thread as either a {@linkplain #isDaemon daemon} thread
* or a user thread. The Java Virtual Machine exits when the only
* threads running are all daemon threads.
*
* This method must be invoked before the thread is started.
*
* @param on
* if {@code true}, marks this thread as a daemon thread
*
* @throws IllegalThreadStateException
* if this thread is {@linkplain #isAlive alive}
*
* @throws SecurityException
* if {@link #checkAccess} determines that the current
* thread cannot modify this thread
*/
public final void setDaemon(boolean on) {
checkAccess();
if (isAlive()) {
throw new IllegalThreadStateException();
}
daemon = on;
}
/**
* Tests if this thread is a daemon thread.
*
* @return true if this thread is a daemon thread;
* false otherwise.
* @see #setDaemon(boolean)
*/
public final boolean isDaemon() {
return daemon;
}
/**
* Determines if the currently running thread has permission to
* modify this thread.
*
* If there is a security manager, its checkAccess method
* is called with this thread as its argument. This may result in
* throwing a SecurityException.
*
* @exception SecurityException if the current thread is not allowed to
* access this thread.
* @see SecurityManager#checkAccess(Thread)
*/
public final void checkAccess() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkAccess(this);
}
}
/**
* Returns a string representation of this thread, including the
* thread's name, priority, and thread group.
*
* @return a string representation of this thread.
*/
public String toString() {
ThreadGroup group = getThreadGroup();
if (group != null) {
return "Thread[" + getName() + "," + getPriority() + "," +
group.getName() + "]";
} else {
return "Thread[" + getName() + "," + getPriority() + "," +
"" + "]";
}
}
/**
* Returns true if and only if the current thread holds the
* monitor lock on the specified object.
*
* This method is designed to allow a program to assert that
* the current thread already holds a specified lock:
*
* assert Thread.holdsLock(obj);
*
*
* @param obj the object on which to test lock ownership
* @throws NullPointerException if obj is null
* @return true if the current thread holds the monitor lock on
* the specified object.
* @since 1.4
*/
public static native boolean holdsLock(Object obj)
/**
* Returns an array of stack trace elements representing the stack dump
* of this thread. This method will return a zero-length array if
* this thread has not started, has started but has not yet been
* scheduled to run by the system, or has terminated.
* If the returned array is of non-zero length then the first element of
* the array represents the top of the stack, which is the most recent
* method invocation in the sequence. The last element of the array
* represents the bottom of the stack, which is the least recent method
* invocation in the sequence.
*
* If there is a security manager, and this thread is not
* the current thread, then the security manager's
* checkPermission method is called with a
* RuntimePermission("getStackTrace") permission
* to see if it's ok to get the stack trace.
*
*
Some virtual machines may, under some circumstances, omit one
* or more stack frames from the stack trace. In the extreme case,
* a virtual machine that has no stack trace information concerning
* this thread is permitted to return a zero-length array from this
* method.
*
* @return an array of StackTraceElement,
* each represents one stack frame.
*
* @throws SecurityException
* if a security manager exists and its
* checkPermission method doesn't allow
* getting the stack trace of thread.
* @see SecurityManager#checkPermission
* @see RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public StackTraceElement[] getStackTrace() {...}
/**
* Returns a map of stack traces for all live threads.
* The map keys are threads and each map value is an array of
* StackTraceElement that represents the stack dump
* of the corresponding Thread.
* The returned stack traces are in the format specified for
* the {@link #getStackTrace getStackTrace} method.
*
* The threads may be executing while this method is called.
* The stack trace of each thread only represents a snapshot and
* each stack trace may be obtained at different time. A zero-length
* array will be returned in the map value if the virtual machine has
* no stack trace information about a thread.
*
*
If there is a security manager, then the security manager's
* checkPermission method is called with a
* RuntimePermission("getStackTrace") permission as well as
* RuntimePermission("modifyThreadGroup") permission
* to see if it is ok to get the stack trace of all threads.
*
* @return a Map from Thread to an array of
* StackTraceElement that represents the stack trace of
* the corresponding thread.
*
* @throws SecurityException
* if a security manager exists and its
* checkPermission method doesn't allow
* getting the stack trace of thread.
* @see #getStackTrace
* @see SecurityManager#checkPermission
* @see RuntimePermission
* @see Throwable#getStackTrace
*
* @since 1.5
*/
public static Map<Thread, StackTraceElement[]> getAllStackTraces() {...}
/**
* Returns the identifier of this Thread. The thread ID is a positive
* long number generated when this thread was created.
* The thread ID is unique and remains unchanged during its lifetime.
* When a thread is terminated, this thread ID may be reused.
*
* @return this thread's ID.
* @since 1.5
*/
public long getId() {
return tid;
}
/**
* A thread state. A thread can be in one of the following states:
*
* - {@link #NEW}
* A thread that has not yet started is in this state.
*
* - {@link #RUNNABLE}
* A thread executing in the Java virtual machine is in this state.
*
* - {@link #BLOCKED}
* A thread that is blocked waiting for a monitor lock
* is in this state.
*
* - {@link #WAITING}
* A thread that is waiting indefinitely for another thread to
* perform a particular action is in this state.
*
* - {@link #TIMED_WAITING}
* A thread that is waiting for another thread to perform an action
* for up to a specified waiting time is in this state.
*
* - {@link #TERMINATED}
* A thread that has exited is in this state.
*
*
*
*
* A thread can be in only one state at a given point in time.
* These states are virtual machine states which do not reflect
* any operating system thread states.
*
* @since 1.5
* @see #getState
*/
public enum State {
/**
* Thread state for a thread which has not yet started.
*/
NEW,
/**
* Thread state for a runnable thread. A thread in the runnable
* state is executing in the Java virtual machine but it may
* be waiting for other resources from the operating system
* such as processor.
*/
RUNNABLE,
/**
* Thread state for a thread blocked waiting for a monitor lock.
* A thread in the blocked state is waiting for a monitor lock
* to enter a synchronized block/method or
* reenter a synchronized block/method after calling
* {@link Object#wait() Object.wait}.
*/
BLOCKED,
/**
* Thread state for a waiting thread.
* A thread is in the waiting state due to calling one of the
* following methods:
*
* - {@link Object#wait() Object.wait} with no timeout
* - {@link #join() Thread.join} with no timeout
* - {@link LockSupport#park() LockSupport.park}
*
*
* A thread in the waiting state is waiting for another thread to
* perform a particular action.
*
* For example, a thread that has called Object.wait()
* on an object is waiting for another thread to call
* Object.notify() or Object.notifyAll() on
* that object. A thread that has called Thread.join()
* is waiting for a specified thread to terminate.
*/
WAITING,
/**
* Thread state for a waiting thread with a specified waiting time.
* A thread is in the timed waiting state due to calling one of
* the following methods with a specified positive waiting time:
*
* - {@link #sleep Thread.sleep}
* - {@link Object#wait(long) Object.wait} with timeout
* - {@link #join(long) Thread.join} with timeout
* - {@link LockSupport#parkNanos LockSupport.parkNanos}
* - {@link LockSupport#parkUntil LockSupport.parkUntil}
*
*/
TIMED_WAITING,
/**
* Thread state for a terminated thread.
* The thread has completed execution.
*/
TERMINATED;
}
/**
* 获取线程当前的状态
*/
public State getState() {
// get current thread state
return sun.misc.VM.toThreadState(threadStatus);
}
}