多線程中等待/通知模式最經(jīng)典的案例就是“生產(chǎn)者/消費者”模式吕座。但此模式在使用上有幾種“變形”撞牢，還有一些小的注意事項缘薛，但原理是基于wait/notify的面徽。該模式可以通過操作值來實現(xiàn)泞边。
一生產(chǎn)與一消費
代碼清單1
//生產(chǎn)者
public class P {
private String lock;
public P(String lock) {
super();
this.lock = lock;
}
public void setValue() {
try {
synchronized (lock) {
if (!ValueObject.value.equals("")) {
lock.wait();
}
String value = System.currentTimeMillis() + "_" + System.nanoTime();
System.out.println("set的值是" + value);
ValueObject.value = value;
lock.notify();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//消費者
public class C {
private String lock;
public C(String lock) {
super();
this.lock = lock;
}
public void getValue() {
try {
synchronized (lock) {
if (ValueObject.value.equals("")) {
lock.wait();
}
System.out.println("get的值是" + ValueObject.value);
ValueObject.value = "";
lock.notify();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//存儲值的對象
public class ValueObject {
public static String value = "";
}
//生產(chǎn)者線程
public class ThreadP extends Thread {
private P p;
public ThreadP(P p) {
super();
this.p = p;
}
@Override
public void run() {
while (true) {
p.setValue();
}
}
}
//消費者線程
public class ThreadC extends Thread {
private C r;
public ThreadC(C r) {
super();
this.r = r;
}
@Override
public void run() {
while (true) {
r.getValue();
}
}
}
//運行類
public class Run {
public static void main(String[] args) {
String lock = new String("");
P p = new P(lock);
C r = new C(lock);
ThreadP pThread = new ThreadP(p);
ThreadC rThread = new ThreadC(r);
pThread.start();
rThread.start();
}
}
運行結(jié)果
set的值是1514222349229_7168218698116
get的值是1514222349229_7168218698116
set的值是1514222349231_7168221053134
get的值是1514222349231_7168221053134
...
本示例是一個生產(chǎn)者和一個消費者進行數(shù)據(jù)的交互馍资，在控制臺中打印的日志set與get是交替運行的穴店。
多生產(chǎn)與多消費
代碼清單2
//生產(chǎn)者
public class P {
private String lock;
public P(String lock) {
super();
this.lock = lock;
}
public void setValue() {
try {
synchronized (lock) {
while (!ValueObject.value.equals("")) {
System.out.println("生產(chǎn)者 "
+ Thread.currentThread().getName() + " WAITING了★");
lock.wait();
}
System.out.println("生產(chǎn)者 " + Thread.currentThread().getName()
+ " RUNNABLE了");
String value = System.currentTimeMillis() + "_"
+ System.nanoTime();
ValueObject.value = value;
lock.notifyAll();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//消費者
public class C {
private String lock;
public C(String lock) {
super();
this.lock = lock;
}
public void getValue() {
try {
synchronized (lock) {
while (ValueObject.value.equals("")) {
System.out.println("消費者"
+ Thread.currentThread().getName() + " WAITING了☆");
lock.wait();
}
System.out.println("消費者" + Thread.currentThread().getName()
+ " RUNNABLE了");
ValueObject.value = "";
lock.notifyAll();
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
//生產(chǎn)者線程
public class ThreadP extends Thread {
private P p;
public ThreadP(P p) {
super();
this.p = p;
}
@Override
public void run() {
while (true) {
p.setValue();
}
}
}
//消費者x
public class ThreadC extends Thread {
private C r;
public ThreadC(C r) {
super();
this.r = r;
}
@Override
public void run() {
while (true) {
r.getValue();
}
}
}
public class ValueObject {
public static String value = "";
}
public class Run {
public static void main(String[] args) throws InterruptedException {
String lock = new String("");
P p = new P(lock);
C r = new C(lock);
ThreadP[] pThread = new ThreadP[2];
ThreadC[] rThread = new ThreadC[2];
for (int i = 0; i < 2; i++) {
pThread[i] = new ThreadP(p);
pThread[i].setName("生產(chǎn)者" + (i + 1));
rThread[i] = new ThreadC(r);
rThread[i].setName("消費者" + (i + 1));
pThread[i].start();
rThread[i].start();
}
Thread.sleep(5000);
Thread[] threadArray = new Thread[Thread.currentThread()
.getThreadGroup().activeCount()];
Thread.currentThread().getThreadGroup().enumerate(threadArray);
for (int i = 0; i < threadArray.length; i++) {
System.out.println(threadArray[i].getName() + " "
+ threadArray[i].getState());
}
}
}
運行結(jié)果
生產(chǎn)者 生產(chǎn)者1 RUNNABLE了
生產(chǎn)者 生產(chǎn)者1 WAITING了★
消費者消費者1 RUNNABLE了
消費者消費者1 WAITING了☆
消費者消費者2 WAITING了☆
生產(chǎn)者 生產(chǎn)者2 RUNNABLE了
生產(chǎn)者 生產(chǎn)者2 WAITING了★
消費者消費者2 RUNNABLE了
消費者消費者2 WAITING了☆
消費者消費者1 WAITING了☆
生產(chǎn)者 生產(chǎn)者1 RUNNABLE了
生產(chǎn)者 生產(chǎn)者1 WAITING了★
...
注意事項
比較上面兩種模式琢岩，主要改動了兩處投剥。
- if()判斷改為while()循環(huán)，重新判斷條件担孔，避免邏輯混亂;
- notify()改為notifyAll()避免進入“假死”狀態(tài)江锨。
本文屬5IYXX原創(chuàng)，轉(zhuǎn)載請注明(http://www.reibang.com/p/82f3f4f1cf00)
