上并发
在并发传递值一点背景是容易的部分。查看AtomicInteger
数据类型(更多信息here)。原子性也意味着All or nothing
。这种数据类型不一定在线程或处理器之间发送数据(就像你使用mpi
一样),但它只是在共享内存上共享数据。
但什么是原子操作?....
原子操作是作为一个独立的工作单元,不受其他业务干扰的可能性进行操作。
在Java中,语言规范保证读取或写入变量是原子的(除非变量的类型是long或double)。龙和双只有原子的,如果他们声明为volatile ....
信贷(Java Concurrency/Multithreading - Tutorial拉尔斯沃格尔)
我强烈建议你阅读这一点,它涵盖了从atomicity
,thread pools
,deadlocks
和the "volatile" and "synchronized" keyword
。
开始授课这将执行一个新的线程(它也可以作为我们Main Thread
简称)。
import java.util.concurrent.atomic.AtomicInteger;
/**
* @author Michael Jones
* @description Main Thread
*/
public class start {
private AtomicInteger state;
private Thread p;
private Thread r;
/**
* constructor
* initialize the declared threads
*/
public start(){
//initialize the state
this.state = new AtomicInteger(0);
//initialize the threads r and p
this.r = new Thread(new action("resume", state));
this.p = new Thread(new action("pause", state));
} //close constructor
/**
* Start the threads
* @throws InterruptedException
*/
public void startThreads() throws InterruptedException{
if(!this.r.isAlive()){
r.start(); //start r
}
if(!this.p.isAlive()){
Thread.sleep(1000); //wait a little (wait for r to update)...
p.start(); //start p
}
} //close startThreads
/**
* This method starts the main thread
* @param args
*/
public static void main(String[] args) {
//call the constructor of this class
start s = new start();
//try the code
try {
s.startThreads();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} //start the threads
} //close main
} //close class start
因为整数是原子,你也可以找回任何地方,但在开始类main method
与System.out.println("[run start] current state is... "+state.intValue());
。(如果您想从main method
找回它,你将不得不建立一个setter /吸气,就像我在Action类这样做)
行动类这是我们在行动主题(它也可以被称为我们的Slave Thread
)。
import java.lang.Thread.State;
import java.util.concurrent.atomic.AtomicInteger;
/**
* @author Michael Jones
* @description Slave Thread
*/
public class action implements Runnable {
private String event = "";
private AtomicInteger state;
/**
* The constructor (this represents the current instance of a thread).
*
* @param event
* @param state
*/
public action(String event, AtomicInteger state) {
this.event = event; // update this instance of event
this.state = state; // update this instance of state
} // constructor
/**
* This method will be called after YourThreadName.Start();
*/
@Override
public void run() {
if (this.event == "resume") {
this.OnResume(); // call resume
} else {
this.OnPause(); // call pause
}
} // close Runnable run() method
/**
* The resume function Use the auto lock from synchronized
*/
public synchronized void OnResume() {
System.out.println("[OnResume] The state was.." + this.getAtomicState()
+ " // Thread: " + Thread.currentThread().getId());
this.setAtomicState(2); // change the state
System.out.println("[OnResume] The state is.." + this.getAtomicState()
+ " // Thread: " + Thread.currentThread().getId());
} // close function
/**
* The pause function Use the auto lock from synchronized
*/
public synchronized void OnPause() {
System.out.println("[OnPause] The state was.." + this.getAtomicState()
+ " // Thread: " + Thread.currentThread().getId());
this.setAtomicState(1); // change the state
System.out.println("[OnPause] The state is.." + this.getAtomicState()
+ " // Thread: " + Thread.currentThread().getId());
} // close function
/**
* Get the atomic integer from memory
*
* @return Integer
*/
private Integer getAtomicState() {
return state.intValue();
}// close function
/**
* Update or Create a new atomic integer
*
* @param value
*/
private void setAtomicState(Integer value) {
if (this.state == null) {
state = new AtomicInteger(value);
} else
state.set(value);
} // close function
} // close the class
控制台输出
[OnResume] The state was..0 // Thread: 9
[OnResume] The state is..2 // Thread: 9
[OnPause] The state was..2 // Thread: 10
[OnPause] The state is..1 // Thread: 10
正如你所看到的,AtomicInteger state
被在内存共享我们的线程r
和p
之间。
解决方案和事情,寻找...
你必须注意的时候做的并发Race Conditions
/Deadlocks
/Livelocks
的唯一的事情。一些RaceConditions
发生是因为Threads
是以随机顺序创建的(并且大多数程序员认为顺序排列的思维集合)。
我也行Thread.sleep(1000);
让我Main Thread
给出了从线程r
一点时间来更新state
(允许p
运行之前),由于线程的随机顺序。
1)保留对线程的引用并将值传递给方法。 信贷(SJuan76,2012)
在我已经发布了解决方案,我让我的Main Thread
(又名class start
)作为我的主要传播者,以跟踪Atomic Integer
为我的奴隶使用(又名class action
)。我的主线也是updating
我的奴隶(内存缓冲区的更新发生在应用程序的后台,由AtomicInteger
类处理)。
我已经更新了我的答案,2个类和'AtomicInteger'的工作实现。问候 – Killrawr 2012-07-24 03:12:24