线程通信用来保证线程协调运行，一般在做线程同步的时候才需要考虑线程通信的问题。
1、传统的线程通信
通常利用Objeclt类提供的三个方法：
这三个方法必须由同步监视器对象调用，分为两张情况：
同步方法时，由于同步监视器为this对象，所以可以直接调用这三个方法。
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) {
//实现两个线程轮流对数据进行加一操作
DataWrap dataWrap = new DataWrap();
new ThreadA(dataWrap).start();
new ThreadB(dataWrap).start();
}
}
同步代码块时，需要使用监视器对象调用这三个方法。
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) {
//实现两个线程轮流对数据进行加一操作
DataWrap dataWrap = new DataWrap();
new ThreadA(dataWrap).start();
new ThreadB(dataWrap).start();
}
}
2、使用Condition控制线程通信
当使用Lock对象保证同步时，则使用Condition对象来保证协调。
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) {
//实现两个线程轮流对数据进行加一操作
DataWrap dataWrap = new DataWrap();
new ThreadA(dataWrap).start();
new ThreadB(dataWrap).start();
}
}
其中Condition对象的await(), singal(),singalAll()分别对应wait(),notify()和notifyAll()方法。
3、使用阻塞队列BlockingQueue控制线程通信
BlockingQueue是Queue接口的子接口，主要用来做线程通信使用，它具有一个特征：当生产者线程试图向BlockingQueue中放入元素时，如果队列已满，则该线程被阻塞；当消费者线程试图从BlockingQueue中取出元素时，如果队列已空，则该线程被阻塞。这两个特征分别对应两个支持阻塞的方法，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) {
///实现两个线程轮流对数据进行加一操作
DataWrap dataWrap = new DataWrap();
BlockingQueue<DataWrap> blockingQueue = new ArrayBlockingQueue<>(1);
new ThreadA(blockingQueue, "Consumer").start();
new ThreadB(blockingQueue, dataWrap, "Producer").start();
}
}
BlockingQueue共有五个实现类：
ArrayBlockingQueue 基于数组实现的BlockingQueue队列
LinkedBlockingQueue 基于链表实现的BlockingQueue队列
PriorityBlockingQueue 中元素需实现Comparable接口，其中元素的排序是按照Comparator进行的定制排序。
SynchronousQueue 同步队列，要求对该队列的存取操作必须是交替进行。
DelayQueue 集合元素必须实现Delay接口，队列中元素排序按照Delay接口方法getDelay()的返回值进行排序。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。
