FutureTask原始碼分析

private

volatile
int state; //
任務狀態
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;
//run正常執行：new -> completing -> normal
//run異常執行：new -> completing -> exceptional
//cancel(false)：new -> cancelled
//cancel(true)：new -> interrupting -> interrupted
private callablecallable; //
任務private object outcome; //
執行結果
private
volatile thread runner; //
任務執行執行緒（在run方法中置為當前執行緒）
private
volatile waitnode waiters; //
任務等待鍊錶（頭節點）

public futuretask(callablecallable) 

public
futuretask(runnable runnable, v result)

static

final
class
waitnode 
}

public

booleancancel(boolean
mayinterruptifrunning) finally}} 
finally
return
true;}
private
void
finishcompletion() 
waitnode next = q.next;
if (next == null
) 
break
; q.next = null
; q =next;
}break
; }
}done(); 
//noop
callable = null;
}protected
void done()

public

booleaniscancelled() 
public
booleanisdone()

public vget() throws

interruptedexception, executionexception 
public v get(long timeout, timeunit unit) throws
interruptedexception, executionexception, timeoutexception 
private
intawaitdone(boolean timed, long nanos) throws
interruptedexception 
int s =state;
if (s > completing) 

else
if (s == completing) //
任務執行中thread.yield();
else

if (q == null) //
任務尚未執行（s == new），則建立任務等待節點qq = new waitnode();else

if (!queued) //
q尚未排隊，則cas設定q為頭節點queued = unsafe.compareandswapobject(this, waitersoffset, q.next = waiters, q);else

if (timed)locksupport.parknanos(this, nanos); //

在naos時間內等待}
elselocksupport.park(

this); //
永久等待}
}private
void
removewaiter(waitnode node) 
// q已被喚醒 && q前不存在未被喚醒節點，則cas設定頭節點為q.nextelse

if (!unsafe.compareandswapobject(this, waitersoffset, q, s))continue
retry;
}break
; }
}}

public

void
run() catch(throwable ex) 

if(ran)set(result);//

設定正常的執行結果}
} finally
}protected
void
set(v v) 
}protected
void
setexception(throwable t) 
}private
void handlepossiblecancellationinterrupt(int
s)

private

static
final
sun.misc.unsafe unsafe;
private
static
final
long
stateoffset;
private
static
final
long
runneroffset;
private
static
final
long
waitersoffset;
static
catch
(exception e) 
}

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