http://blog.csdn.net/aboy123/article/details/38307539
runnable与callable区别：
https://www.cnblogs.com/frinder6/p/5507082.html
callable与futurTask实现：
package com.hailong.hailongTest.thread;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;
import com.hailong.hailongTest.InsertSort;
import com.hailong.hailongTest.SelectSort;
public class UserServiceByFuture {
public static Map<String, String> UserServiceByFuture(final int[] testInts1, final int[] testInts2) {
// InsertSort insertSort = new InsertSort();
// SelectSort selectSort = new SelectSort();
// Map<String, String> result = new HashMap<String, String>();
// result.put("a", insertSort.getInsertSort(testInts1));
// result.put("b", selectSort.getSelectSort(testInts2));
//-----------------------------------------------------------
Callable<String> callableString = new Callable<String>() {
public String call() throws Exception {
InsertSort insertSort = new InsertSort();
return insertSort.getInsertSort(testInts1);
// TODO Auto-generated method stub
}
};
FutureTask<String> futureTask = new FutureTask<String>(callableString);
new Thread(futureTask).start();
//-----------------------------------------------------------
Callable<String> callableString2 = new Callable<String>() {
public String call() throws Exception {
SelectSort selectSort = new SelectSort();
return selectSort.getSelectSort(testInts2);
// TODO Auto-generated method stub
}
};
FutureTask<String> futureTask2 = new FutureTask<String>(callableString2);
new Thread(futureTask2).start();
//-----------------------------------------------------------
Map<String, String> result = new HashMap<String, String>();
try {
result.put("a", futureTask.get());
result.put("b", futureTask2.get());
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ExecutionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return result;
}
public static void main(String[] args) {
long currentTime = System.currentTimeMillis();
int[] testInts1 = {1,44,6,2,45,98,45};
int[] testInts2 = {1,44,6,2,45,98,45};
// TODO Auto-generated method stub
Map<String, String> result = UserServiceByFuture(testInts1, testInts2);
System.out.println(result.get("a"));
System.out.println(result.get("b"));
System.out.println(System.currentTimeMillis() - currentTime);
}
}
get()怎样实现阻塞。
执行完之后，如何通知其他线程的。
futureTask的run：
https://www.jianshu.com/p/7ef8be1205ec
futureTask源码分析：
import java.util.concurrent.FutureTask.WaitNode;
import java.util.concurrent.locks.LockSupport;
public class FutureTask<V> implements RunnableFuture<V> {
/**
* The run state of this task, initially NEW. The run state
* transitions to a terminal state only in methods set,
* setException, and cancel. During completion, state may take on
* transient values of COMPLETING (while outcome is being set) or
* INTERRUPTING (only while interrupting the runner to satisfy a
* cancel(true)). Transitions from these intermediate to final
* states use cheaper ordered/lazy writes because values are unique
* and cannot be further modified.
*
* Possible state transitions:
* NEW -> COMPLETING -> NORMAL
* NEW -> COMPLETING -> EXCEPTIONAL
* NEW -> CANCELLED
* NEW -> INTERRUPTING -> INTERRUPTED
*/
private volatile int state;
private static final int NEW = 0;
private static final int COMPLETING = 1;
private static final int NORMAL = 2;
private static final int EXCEPTIONAL = 3;
private static final int CANCELLED = 4;
private static final int INTERRUPTING = 5;
private static final int INTERRUPTED = 6;
/** The underlying callable; nulled out after running */
private Callable<V> callable;
/** The result to return or exception to throw from get() */
private Object outcome; // non-volatile, protected by state reads/writes
/** The thread running the callable; CASed during run() */
private volatile Thread runner;
/** Treiber stack of waiting threads */
private volatile WaitNode waiters;
/**
* Returns result or throws exception for completed task.
*
* @param s completed state value
*/
@SuppressWarnings("unchecked")
private V report(int s) throws ExecutionException {
Object x = outcome;
if (s == NORMAL)
return (V)x;
if (s >= CANCELLED)
throw new CancellationException();
throw new ExecutionException((Throwable)x);
}
/**
* Creates a {@code FutureTask} that will, upon running, execute the
* given {@code Callable}.
*
* @param callable the callable task
* @throws NullPointerException if the callable is null
*/
public FutureTask(Callable<V> callable) {
if (callable == null)
throw new NullPointerException();
this.callable = callable;
this.state = NEW; // ensure visibility of callable
}
/**
* Creates a {@code FutureTask} that will, upon running, execute the
* given {@code Runnable}, and arrange that {@code get} will return the
* given result on successful completion.
*
* @param runnable the runnable task
* @param result the result to return on successful completion. If
* you don't need a particular result, consider using
* constructions of the form:
* {@code Future<?> f = new FutureTask<Void>(runnable, null)}
* @throws NullPointerException if the runnable is null
*/
public FutureTask(Runnable runnable, V result) {
this.callable = Executors.callable(runnable, result);
this.state = NEW; // ensure visibility of callable
}
public boolean isCancelled() {
return state >= CANCELLED;
}
public boolean isDone() {
return state != NEW;
}
// 只能取消还没被执行的任务(任务状态为NEW的任务)- cancel(boolean)
public boolean cancel(boolean mayInterruptIfRunning) {
// 只有刚创建的情况才能取消
if (state != NEW)
return false;
// ture：中断，false：取消
if (mayInterruptIfRunning) {
// 继续判断任务的当前状态是否为NEW,因为此时执行任务线程可能再度获得处理了,任务状态可能已发生改变
if (!UNSAFE.compareAndSwapInt(this, stateOffset, NEW, INTERRUPTING))
return false;
// 如果任务状态依然是NEW, 也就是执行线程没有改变任务的状态,
// 则让执行线程中断(在这个过程中执行线程可能会改变任务的状态)
Thread t = runner;
// 对runner 发布interrupt信号
if (t != null)
t.interrupt();
// 修改状态为已经通知线程中断
UNSAFE.putOrderedInt(this, stateOffset, INTERRUPTED); // final state
}
else if (!UNSAFE.compareAndSwapInt(this, stateOffset, NEW, CANCELLED))
return false;
finishCompletion();
return true;
}
/**
* @throws CancellationException {@inheritDoc}
* 获取任务的执行结果-get()方法和get(long,TimeUnit)方法, 核心在于内部调用的awaitDone()方法
*/
public V get() throws InterruptedException, ExecutionException {
int s = state;
if (s <= COMPLETING)
s = awaitDone(false, 0L);
return report(s);
}
/**
* @throws CancellationException {@inheritDoc}
*/
public V get(long timeout, TimeUnit unit)
throws InterruptedException, ExecutionException, TimeoutException {
if (unit == null)
throw new NullPointerException();
int s = state;
if (s <= COMPLETING &&
(s = awaitDone(true, unit.toNanos(timeout))) <= COMPLETING)
throw new TimeoutException();
return report(s);
}
/**
* Sets the result of this future to the given value unless
* this future has already been set or has been cancelled.
*
* <p>This method is invoked internally by the {@link #run} method
* upon successful completion of the computation.
*
* @param v the value
*/
protected void set(V v) {
// 首先将任务的状态改变
// 状态改变成功之后再将结果赋值
// 赋值成功,改变任务的状态
// 处理等待线程队列(将线程阻塞状态改为唤醒,这样哪些等待获取结果的线程就可以取得任务结果)
if (UNSAFE.compareAndSwapInt(this, stateOffset, NEW, COMPLETING)) {
outcome = v;
// 修改状态
UNSAFE.putOrderedInt(this, stateOffset, NORMAL); // final state
// 通知其他在等待结果的线程
finishCompletion();
}
}
/**
* Causes this future to report an {@link ExecutionException}
* with the given throwable as its cause, unless this future has
* already been set or has been cancelled.
*
* <p>This method is invoked internally by the {@link #run} method
* upon failure of the computation.
*
* @param t the cause of failure
*/
protected void setException(Throwable t) {
if (UNSAFE.compareAndSwapInt(this, stateOffset, NEW, COMPLETING)) {
outcome = t;
// 修改为异常状态
UNSAFE.putOrderedInt(this, stateOffset, EXCEPTIONAL); // final state
// 通知其他在等待结果的线程
finishCompletion();
}
}
public void run() {
// 判断状态来设置futuretask归属线程
// 1.判断任务的状态是否是初始化状态
// 2.判断执行任务的线程对象runner是否为空,为空就将当前执行线程赋值给runner属性
if (state != NEW ||
!UNSAFE.compareAndSwapObject(this, runnerOffset,
null, Thread.currentThread()))
return;
try {
Callable<V> c = callable;
// 任务状态是NEW, 并且callable不为空(在任务被cancel()时,callable会被置空)则执行任务
if (c != null && state == NEW) {
V result;
boolean ran;
try {
// 执行任务,返回结果
result = c.call();
// 标记执行成功
ran = true;
} catch (Throwable ex) {
result = null;
ran = false;
// 设置为异常状态，并通知其他在等待结果的线程
setException(ex);
}
// 执行成功，修改状态为成功，并通知其他在等待结果的线程
if (ran)
set(result);
}
} finally {
// runner must be non-null until state is settled to
// prevent concurrent calls to run()
runner = null;
// state must be re-read after nulling runner to prevent
// leaked interrupts
int s = state;
if (s >= INTERRUPTING)
// 如果状态为发起中断信号（INTERRUPTING = 5）或已经中断信号（INTERRUPTED = 6）
// 让出cpu（）
handlePossibleCancellationInterrupt(s);
}
}
/**
* Executes the computation without setting its result, and then
* resets this future to initial state, failing to do so if the
* computation encounters an exception or is cancelled. This is
* designed for use with tasks that intrinsically execute more
* than once.
*
* @return true if successfully run and reset
*/
protected boolean runAndReset() {
if (state != NEW ||
!UNSAFE.compareAndSwapObject(this, runnerOffset,
null, Thread.currentThread()))
return false;
boolean ran = false;
int s = state;
try {
Callable<V> c = callable;
if (c != null && s == NEW) {
try {
c.call(); // don't set result
ran = true;
} catch (Throwable ex) {
setException(ex);
}
}
} finally {
// runner must be non-null until state is settled to
// prevent concurrent calls to run()
runner = null;
// state must be re-read after nulling runner to prevent
// leaked interrupts
s = state;
if (s >= INTERRUPTING)
handlePossibleCancellationInterrupt(s);
}
return ran && s == NEW;
}
/**
* Removes and signals all waiting threads, invokes done(), and
* nulls out callable.
* 在任务执行完成(包括取消、正常结束、发生异常), 将等待线程列表唤醒
* 同时让任务执行体置空
*/
private void finishCompletion() {
// assert state > COMPLETING;
for (WaitNode q; (q = waiters) != null;) {
if (UNSAFE.compareAndSwapObject(this, waitersOffset, q, null)) {
for (;;) {
Thread t = q.thread;
if (t != null) {
q.thread = null;
LockSupport.unpark(t);
}
WaitNode next = q.next;
if (next == null)
break;
q.next = null; // unlink to help gc
q = next;
}
break;
}
}
done();
callable = null; // to reduce footprint
}
/**
* Awaits completion or aborts on interrupt or timeout.
*
* @param timed true if use timed waits
* @param nanos time to wait, if timed
* @return state upon completion
* 等待任务的执行结果
* timed: 是否有时间限制 nanos: 限制的时间
*/
private int awaitDone(boolean timed, long nanos)
throws InterruptedException {
// 计算限制的时间范围,记录等待的超时
final long deadline = timed ? System.nanoTime() + nanos : 0L;
// 当前等待线程节点
// 多个在等待结果的线程，通过一个链表进行保存，WaitNode就是每个线程在链表节点
WaitNode q = null;
// 是否将节点放在了等待列表中
boolean queued = false;
// 无限循环来实现线程阻塞等待，自扰锁同步
for (;;) {
// 判断当前线程是否被中断
if (Thread.interrupted()) {
// 当前线程移出队列
removeWaiter(q);
throw new InterruptedException();
}
int s = state;
// 1. 首先判断任务状态是否是完成状态, 如果完成, 是就直接返回结果
if (s > COMPLETING) {
if (q != null)
q.thread = null;
return s;
}
// 2. 如果1为false,并且任务的状态是COMPLETING（已执行，但没有结束）, 也就是在set()任务结果时被阻塞了,则让出当前线程cpu资源
else if (s == COMPLETING) // cannot time out yet
Thread.yield();
// 3. 如果前两步false,并且q==null,则初始化一个当前线程的等待节点
else if (q == null)
q = new WaitNode();
// 4. 下一次循环体, 如果前3步依然是false,并且当前节点没有加入到等待列表,
// 则将当前线程节点放在等待列表的第一个位置
// 如果当前线程对应的WaitNode还没有加入到等待链表中，就加进去
else if (!queued)
queued = UNSAFE.compareAndSwapObject(this, waitersOffset,
q.next = waiters, q);
// 5. 在下一次循环, 如果前4步为false, 如果是时间范围内等待的,则判断当前时间是否过期,
// 过期则将线程节点移出等待队列并返回任务状态结果, 如果没过期,则让当前线程阻塞一定时间
// 通过parkNanos挂起当前线程，等待继续执行信号。
else if (timed) {
nanos = deadline - System.nanoTime();
if (nanos <= 0L) {
removeWaiter(q);
return state;
}
LockSupport.parkNanos(this, nanos);
}
// 6. 如果不是时间范围内等待, 并且前5步均为false,则让线程阻塞,直到被唤醒
// 通过pack挂起当前线程，等待task run执行结束发送执行信号（unpack）
else
LockSupport.park(this);
}
}
/**
* Tries to unlink a timed-out or interrupted wait node to avoid
* accumulating garbage. Internal nodes are simply unspliced
* without CAS since it is harmless if they are traversed anyway
* by releasers. To avoid effects of unsplicing from already
* removed nodes, the list is retraversed in case of an apparent
* race. This is slow when there are a lot of nodes, but we don't
* expect lists to be long enough to outweigh higher-overhead
* schemes.
* 将线程节点从等待队列中移出
*/
private void removeWaiter(WaitNode node) {
if (node != null) {
node.thread = null;
retry:
for (;;) { // restart on removeWaiter race
for (WaitNode pred = null, q = waiters, s; q != null; q = s) {
s = q.next;
if (q.thread != null)
pred = q;
else if (pred != null) {
pred.next = s;
if (pred.thread == null) // check for race
continue retry;
}
else if (!UNSAFE.compareAndSwapObject(this, waitersOffset,
q, s))
continue retry;
}
break;
}
}
}
}
wait/notify 有顺序的。
park/unpark挂起线程，一次性的，与先后顺序无关。灵活
park（a）;
unpark（a）;
ExecutorService对象原理简析：
http://blog.csdn.net/lu123535884/article/details/49495833
线程池 submit execute区别
http://blog.csdn.net/u010940300/article/details/50251841
感想思考：
线程状态有哪些，如何变化的。
调用了interrupt就能中断线程吗。
阅读jdk或spring源码正确方式。