说实话，这部分东西太多了，而且涉及到JNI和JVM的东西，先只分析一小部分，以后再补上
//runnable是只有一个run函数的接口
public
class Thread implements Runnable {
/* Make sure registerNatives is the first thing <clinit> does. */
//jni
private static native void registerNatives();
static {
registerNatives();
}
private char name[];
private int priority;
private Thread threadQ;
private long eetop;
/* Whether or not to single_step this thread. */
private boolean single_step;
/* Whether or not the thread is a daemon thread. */
/*是否是守护线程，只有当父线程是守护线程时，该线程就会自动变为守护线程*/
private boolean daemon = false;
/* JVM state */
private boolean stillborn = false;
/* What will be run. */
private Runnable target;
/* The group of this thread */
private ThreadGroup group;
/* The context ClassLoader for this thread */
private ClassLoader contextClassLoader;
/* The inherited AccessControlContext of this thread */
private AccessControlContext inheritedAccessControlContext;
/* For autonumbering anonymous threads. */
private static int threadInitNumber;
/*用于分配线程的id号，注意这里的synchronized*/
private static synchronized int nextThreadNum() {
return threadInitNumber++;
}
/* ThreadLocal values pertaining to this thread. This map is maintained
* by the ThreadLocal class. */
ThreadLocal.ThreadLocalMap threadLocals = null;
/*
* InheritableThreadLocal values pertaining to this thread. This map is
* maintained by the InheritableThreadLocal class.
*/
ThreadLocal.ThreadLocalMap inheritableThreadLocals = null;
/*
* The requested stack size for this thread, or 0 if the creator did
* not specify a stack size. It is up to the VM to do whatever it
* likes with this number; some VMs will ignore it.
*/
private long stackSize;
/*
* JVM-private state that persists after native thread termination.
*/
private long nativeParkEventPointer;
/*
* Thread ID
*/
/*用于内部表示的线程号*/
private long tid;
/* For generating thread ID */
private static long threadSeqNumber;
/* Java thread status for tools,
* initialized to indicate thread 'not yet started'
*/
private int threadStatus = 0;
/*分配线程内部的线程号*/
private static synchronized long nextThreadID() {
return ++threadSeqNumber;
}
/**
* The argument supplied to the current call to
* java.util.concurrent.locks.LockSupport.park.
* Set by (private) java.util.concurrent.locks.LockSupport.setBlocker
* Accessed using java.util.concurrent.locks.LockSupport.getBlocker
*/
volatile Object parkBlocker;
/* The object in which this thread is blocked in an interruptible I/O
* operation, if any. The blocker's interrupt method should be invoked
* after setting this thread's interrupt status.
*/
private volatile Interruptible blocker;
private Object blockerLock = new Object();
/* Set the blocker field; invoked via sun.misc.SharedSecrets from java.nio code
*/
void blockedOn(Interruptible b) {
synchronized (blockerLock) {
blocker = b;
}
}
/**
* 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;
/* If stop was called before start */
private boolean stopBeforeStart;
/* Remembered Throwable from stop before start */
private Throwable throwableFromStop;
/* Whether or not the Thread has been completely constructed;
* init or clone method has successfully completed */
private volatile Thread me; // null
/*下面是一些线程控制的jni*/
/**
* Returns a reference to the currently executing thread object.
*
* @return the currently executing thread.
*/
public static native Thread currentThread();
/**
* Causes the currently executing thread object to temporarily pause
* and allow other threads to execute.
*/
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.
* @exception 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.
* @see Object#notify()
*/
public static native void sleep(long millis) throws InterruptedException;
/**
* Causes the currently executing thread to sleep (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 0-999999 additional nanoseconds to sleep.
* @exception IllegalArgumentException if the value of millis is
* negative or the value of nanos is not in the range
* 0-999999.
* @exception 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.
* @see Object#notify()
*/
public static void sleep(long millis, int nanos)
throws InterruptedException {
/*参数检查*/
if (millis < 0) {
throw new IllegalArgumentException("timeout value is negative");
}
if (nanos < 0 || nanos > 999999) {
throw new IllegalArgumentException(
"nanosecond timeout value out of range");
}
/*将纳秒约到毫秒上去*/
if (nanos >= 500000 || (nanos != 0 && millis == 0)) {
millis++;
}
/*调用sleep的jni*/
sleep(millis);
}
/**
* Initializes a Thread.
*
* @param g the Thread group
* @param target the object whose run() method gets called
* @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.
*/
private void init(ThreadGroup g, Runnable target, String name,
long stackSize) {
/*当前的线程会成为创建后的线程的父线程*/
Thread parent = currentThread();
SecurityManager security = System.getSecurityManager();
/*设置线程组*/
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. */
/*进行权限检查*/
g.checkAccess();
/*
* Do we have the required permissions?
*/
if (security != null) {
if (isCCLOverridden(getClass())) {
security.checkPermission(SUBCLASS_IMPLEMENTATION_PERMISSION);
}
}
g.addUnstarted();
/*设置属性*/
this.group = g;
this.daemon = parent.isDaemon();
this.priority = parent.getPriority();
this.name = name.toCharArray();
/*线程上下文的获取*/
if (security == null || isCCLOverridden(parent.getClass()))
this.contextClassLoader = parent.getContextClassLoader();
else
this.contextClassLoader = parent.contextClassLoader;
this.inheritedAccessControlContext = AccessController.getContext();
/*设置线程的运行函数*/
this.target = target;
/*设置线程的优先级*/
setPriority(priority);
if (parent.inheritableThreadLocals != null)
this.inheritableThreadLocals =
ThreadLocal.createInheritedMap(parent.inheritableThreadLocals);
/* Stash the specified stack size in case the VM cares */
/*设置堆栈的大小*/
this.stackSize = stackSize;
/* Set thread ID */
/*分配内部表示的线程号*/
tid = nextThreadID();
/*设置自身，标记已经初始化*/
this.me = this;
}
/**
* Returns a clone if the class of this object is {@link Cloneable Cloneable}.
*
* @return a clone if the class of this object is {@code Cloneable}
*
* @throws CloneNotSupportedException
* if this method is invoked on a class that does not
* support {@code Cloneable}
*/
/*重载object的clone函数*/
@Override
protected Object clone() throws CloneNotSupportedException {
Thread t;
synchronized(this) {
t = (Thread) super.clone();
/*分配一个新的线程号*/
t.tid = nextThreadID();
t.parkBlocker = null;
t.blocker = null;
t.blockerLock = new Object();
t.threadLocals = null;
/**/
group.checkAccess();
if (threadStatus == 0) {
group.addUnstarted();
}
t.setPriority(priority);
final Thread current = Thread.currentThread();
if (current.inheritableThreadLocals != null)
t.inheritableThreadLocals =
ThreadLocal.createInheritedMap(current.inheritableThreadLocals);
}
t.me = t;
return t;
}
/*************************一大片构造器即将来袭*****************************/
/**
* Allocates a new <code>Thread</code> object. This constructor has
* the same effect as <code>Thread(null, null,</code>
* <i>gname</i><code>)</code>, where <b><i>gname</i></b> is
* a newly generated name. Automatically generated names are of the
* form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
*
* @see #Thread(ThreadGroup, Runnable, String)
*/
public Thread() {
init(null, null, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new <code>Thread</code> object. This constructor has
* the same effect as <code>Thread(null, target,</code>
* <i>gname</i><code>)</code>, where <i>gname</i> is
* a newly generated name. Automatically generated names are of the
* form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
*
* @param target the object whose <code>run</code> method is called.
* @see #Thread(ThreadGroup, Runnable, String)
*/
public Thread(Runnable target) {
init(null, target, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new <code>Thread</code> object. This constructor has
* the same effect as <code>Thread(group, target,</code>
* <i>gname</i><code>)</code>, where <i>gname</i> is
* a newly generated name. Automatically generated names are of the
* form <code>"Thread-"+</code><i>n</i>, where <i>n</i> is an integer.
*
* @param group the thread group.
* @param target the object whose <code>run</code> method is called.
* @exception SecurityException if the current thread cannot create a
* thread in the specified thread group.
* @see #Thread(ThreadGroup, Runnable, String)
*/
public Thread(ThreadGroup group, Runnable target) {
init(group, target, "Thread-" + nextThreadNum(), 0);
}
/**
* Allocates a new <code>Thread</code> object. This constructor has
* the same effect as <code>Thread(null, null, name)</code>.
*
* @param name the name of the new thread.
* @see #Thread(ThreadGroup, Runnable, String)
*/
public Thread(String name) {
init(null, null, name, 0);
}
/**
* Allocates a new <code>Thread</code> object. This constructor has
* the same effect as <code>Thread(group, null, name)</code>
*
* @param group the thread group.
* @param name the name of the new thread.
* @exception SecurityException if the current thread cannot create a
* thread in the specified thread group.
* @see #Thread(ThreadGroup, Runnable, String)
*/
public Thread(ThreadGroup group, String name) {
init(group, null, name, 0);
}
/**
* Allocates a new <code>Thread</code> object. This constructor has
* the same effect as <code>Thread(null, target, name)</code>.
*
* @param target the object whose <code>run</code> method is called.
* @param name the name of the new thread.
* @see #Thread(ThreadGroup, Runnable, String)
*/
public Thread(Runnable target, String name) {
init(null, target, name, 0);
}
/**
* Allocates a new <code>Thread</code> object so that it has
* <code>target</code> as its run object, has the specified
* <code>name</code> as its name, and belongs to the thread group
* referred to by <code>group</code>.
* <p>
* If <code>group</code> is <code>null</code> and there is a
* security manager, the group is determined by the security manager's
* <code>getThreadGroup</code> method. If <code>group</code> is
* <code>null</code> and there is not a security manager, or the
* security manager's <code>getThreadGroup</code> method returns
* <code>null</code>, the group is set to be the same ThreadGroup
* as the thread that is creating the new thread.
*
* <p>If there is a security manager, its <code>checkAccess</code>
* method is called with the ThreadGroup as its argument.
* <p>In addition, its <code>checkPermission</code>
* method is called with the
* <code>RuntimePermission("enableContextClassLoaderOverride")</code>
* permission when invoked directly or indirectly by the constructor
* of a subclass which overrides the <code>getContextClassLoader</code>
* or <code>setContextClassLoader</code> methods.
* This may result in a SecurityException.
* <p>
* If the <code>target</code> argument is not <code>null</code>, the
* <code>run</code> method of the <code>target</code> is called when
* this thread is started. If the target argument is
* <code>null</code>, this thread's <code>run</code> method is called
* when this thread is started.
* <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 <code>setPriority</code> 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 <code>setDaemon </code> may be used
* to change whether or not a thread is a daemon.
*
* @param group the thread group.
* @param target the object whose <code>run</code> method is called.
* @param name the name of the new thread.
* @exception SecurityException if the current thread cannot create a
* thread in the specified thread group or cannot
* override the context class loader methods.
* @see Runnable#run()
* @see #run()
* @see #setDaemon(boolean)
* @see #setPriority(int)
* @see ThreadGroup#checkAccess()
* @see SecurityManager#checkAccess
*/
public Thread(ThreadGroup group, Runnable target, String name) {
init(group, target, name, 0);
}
/**
* Allocates a new <code>Thread</code> object so that it has
* <code>target</code> as its run object, has the specified
* <code>name</code> as its name, belongs to the thread group referred to
* by <code>group</code>, 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
* <tt>stackSize</tt> parameter, if any, is highly platform dependent.</b>
*
* <p>On some platforms, specifying a higher value for the
* <tt>stackSize</tt> 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
* <tt>stackSize</tt> parameter may have no effect whatsoever.</b>
*
* <p>The virtual machine is free to treat the <tt>stackSize</tt>
* 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 <tt>stackSize</tt> parameter will
* cause this constructor to behave exactly like the
* <tt>Thread(ThreadGroup, Runnable, String)</tt> 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
* <tt>stackSize parameter</tt>.
*
* @param group the thread group.
* @param target the object whose <code>run</code> method is called.
* @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.
* @exception 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 <code>run</code> method of this thread.
* <p>
* The result is that two threads are running concurrently: the
* current thread (which returns from the call to the
* <code>start</code> method) and the other thread (which executes its
* <code>run</code> method).
* <p>
* 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()
*/
/*启动线程*/
public synchronized void start() {
/**
* This method is not invoked for the main method thread or "system"
* group threads created/set up by the VM. Any new functionality added
* to this method in the future may have to also be added to the VM.
*
* A zero status value corresponds to state "NEW".
*/
//还没初始化，安能启动啊
if (threadStatus != 0 || this != me)
throw new IllegalThreadStateException();
/*添加到线程组*/
group.add(this);
/*Java啊！你也没有能力调用系统调用啊，还得小JNI来调用系统调用，创建真正的线程啊*/
start0();
/*如果需要不立即执行，就让他停下来*/
if (stopBeforeStart) {
stop0(throwableFromStop);
}
}
private native void start0();
/**
* If this thread was constructed using a separate
* <code>Runnable</code> run object, then that
* <code>Runnable</code> object's <code>run</code> method is called;
* otherwise, this method does nothing and returns.
* <p>
* Subclasses of <code>Thread</code> should override this method.
*
* @see #start()
* @see #stop()
* @see #Thread(ThreadGroup, Runnable, String)
*/
//线程的执行体，要么new Thread(Runnable)设置target，要么就得重载这个函数啊
//Java得多态真好，父类可以调用子类得函数；相比C++就不行了，可能是C++的效率考虑吧
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.
*/
//退出线程
private void exit() {
if (group != null) {
//移出线程组，应该这个函数执行完，线程就终止了吧
group.remove(this);
group = null;
}
//清空所有的域
/* 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;
}