線程通信用來保證線程協(xié)調(diào)運行，一般在做線程同步的時候才需要考慮線程通信的問題。
1、傳統(tǒng)的線程通信
通常利用Objeclt類提供的三個方法：
這三個方法必須由同步監(jiān)視器對象調(diào)用，分為兩張情況：
同步方法時，由于同步監(jiān)視器為this對象，所以可以直接調(diào)用這三個方法。
示例如下：
public class SyncMethodThreadCommunication { static class DataWrap{ int data = 0; boolean flag = false; public synchronized void addThreadA(){ if (flag) { try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } } data++; System.out.println(Thread.currentThread().getName() + " " + data); flag = true; notify(); } public synchronized void addThreadB() { if (!flag) { try { wait(); } catch (InterruptedException e) { e.printStackTrace(); } } data++; System.out.println(Thread.currentThread().getName() + " " + data); flag = false; notify(); } } static class ThreadA extends Thread { private DataWrap data; public ThreadA(DataWrap dataWrap) { this.data = dataWrap; } @Override public void run() { for (int i = 0; i < 10; i++) { data.addThreadA(); } } } static class ThreadB extends Thread { private DataWrap data; public ThreadB(DataWrap dataWrap) { this.data = dataWrap; } @Override public void run() { for (int i = 0; i < 10; i++) { data.addThreadB(); } } } public static void main(String[] args) { //實現(xiàn)兩個線程輪流對數(shù)據(jù)進行加一操作 DataWrap dataWrap = new DataWrap(); new ThreadA(dataWrap).start(); new ThreadB(dataWrap).start(); }}同步代碼塊時，需要使用監(jiān)視器對象調(diào)用這三個方法。
示例如下：
public class SyncBlockThreadComminication { static class DataWrap{ boolean flag; int data; } static class ThreadA extends Thread{ DataWrap dataWrap; public ThreadA(DataWrap dataWrap){ this.dataWrap = dataWrap; } @Override public void run() { for(int i = 0 ; i < 10; i++) { synchronized (dataWrap) { if (dataWrap.flag) { try { dataWrap.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } dataWrap.data++; System.out.println(getName() + " " + dataWrap.data); dataWrap.flag = true; dataWrap.notify(); } } } } static class ThreadB extends Thread{ DataWrap dataWrap; public ThreadB(DataWrap dataWrap){ this.dataWrap = dataWrap; } @Override public void run() { for (int i = 0; i < 10; i++) { synchronized (dataWrap) { if (!dataWrap.flag) { try { dataWrap.wait(); } catch (InterruptedException e) { e.printStackTrace(); } } dataWrap.data++; System.out.println(getName() + " " + dataWrap.data); dataWrap.flag = false; dataWrap.notify(); } } } } public static void main(String[] args) { //實現(xiàn)兩個線程輪流對數(shù)據(jù)進行加一操作 DataWrap dataWrap = new DataWrap(); new ThreadA(dataWrap).start(); new ThreadB(dataWrap).start(); }}2、使用Condition控制線程通信
當使用Lock對象保證同步時，則使用Condition對象來保證協(xié)調(diào)。
示例如下：
import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;import com.sun.media.sound.RIFFInvalidDataException;import javafx.scene.chart.PieChart.Data;public class SyncLockThreadCommunication { static class DataWrap { int data; boolean flag; private final Lock lock = new ReentrantLock(); private final Condition condition = lock.newCondition(); public void addThreadA() { lock.lock(); try { if (flag) { try { condition.await(); } catch (InterruptedException e) { e.printStackTrace(); } } data++; System.out.println(Thread.currentThread().getName() + " " + data); flag = true; condition.signal(); } finally { lock.unlock(); } } public void addThreadB() { lock.lock(); try { if (!flag) { try { condition.await(); } catch (InterruptedException e) { e.printStackTrace(); } } data++; System.out.println(Thread.currentThread().getName() + " " + data); flag = false; condition.signal(); } finally { lock.unlock(); } } } static class ThreadA extends Thread{ DataWrap dataWrap; public ThreadA(DataWrap dataWrap) { this.dataWrap = dataWrap; } @Override public void run() { for (int i = 0; i < 10; i++) { dataWrap.addThreadA(); } } } static class ThreadB extends Thread{ DataWrap dataWrap; public ThreadB(DataWrap dataWrap) { this.dataWrap = dataWrap; } @Override public void run() { for (int i = 0; i < 10; i++) { dataWrap.addThreadB(); } } } public static void main(String[] args) { //實現(xiàn)兩個線程輪流對數(shù)據(jù)進行加一操作 DataWrap dataWrap = new DataWrap(); new ThreadA(dataWrap).start(); new ThreadB(dataWrap).start(); }}其中Condition對象的await(), singal(),singalAll()分別對應wait(),notify()和notifyAll()方法。
3、使用阻塞隊列BlockingQueue控制線程通信
BlockingQueue是Queue接口的子接口，主要用來做線程通信使用，它具有一個特征：當生產(chǎn)者線程試圖向BlockingQueue中放入元素時，如果隊列已滿，則該線程被阻塞；當消費者線程試圖從BlockingQueue中取出元素時，如果隊列已空，則該線程被阻塞。這兩個特征分別對應兩個支持阻塞的方法，put(E e)和take()
示例如下：
import java.util.concurrent.ArrayBlockingQueue;import java.util.concurrent.BlockingQueue;public class BlockingQueueThreadComminication { static class DataWrap{ int data; } static class ThreadA extends Thread{ private BlockingQueue<DataWrap> blockingQueue; public ThreadA(BlockingQueue<DataWrap> blockingQueue, String name) { super(name); this.blockingQueue = blockingQueue; } @Override public void run() { for (int i = 0; i < 100; i++) { try { DataWrap dataWrap = blockingQueue.take(); dataWrap.data++; System.out.println(getName() + " " + dataWrap.data); sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } } static class ThreadB extends Thread{ private BlockingQueue<DataWrap> blockingQueue; private DataWrap dataWrap; public ThreadB(BlockingQueue<DataWrap> blockingQueue, DataWrap dataWrap, String name) { super(name); this.blockingQueue = blockingQueue; this.dataWrap = dataWrap; } @Override public void run() { for (int i = 0; i < 100; i++) { try { dataWrap.data++; System.out.println(getName() + " " + dataWrap.data); blockingQueue.put(dataWrap); sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } } } } public static void main(String[] args) { ///實現(xiàn)兩個線程輪流對數(shù)據(jù)進行加一操作 DataWrap dataWrap = new DataWrap(); BlockingQueue<DataWrap> blockingQueue = new ArrayBlockingQueue<>(1); new ThreadA(blockingQueue, "Consumer").start(); new ThreadB(blockingQueue, dataWrap, "Producer").start(); }}BlockingQueue共有五個實現(xiàn)類：
ArrayBlockingQueue 基于數(shù)組實現(xiàn)的BlockingQueue隊列
LinkedBlockingQueue 基于鏈表實現(xiàn)的BlockingQueue隊列
PriorityBlockingQueue 中元素需實現(xiàn)Comparable接口，其中元素的排序是按照Comparator進行的定制排序。
SynchronousQueue 同步隊列，要求對該隊列的存取操作必須是交替進行。
DelayQueue 集合元素必須實現(xiàn)Delay接口，隊列中元素排序按照Delay接口方法getDelay()的返回值進行排序。
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