Producer-Consumer

摘要: 生产者消费者模式在多线程中运用

Producer-Consumer

很多时候生产者消费者速度不一致且差距比较大的情况下：生产者和消费者多线程设计模式，就可以考虑一下了。最关键的就是中间有一个缓冲的桥梁。(桥梁有两个限制，一个是装不下的情况，一个是取不出的情况)

//生产者代码

public class MakerThread extends Thread {
private final Table table;
private static int id = 0;

public MakerThread(String name, Table table) {
super(name);
this.table = table;

}

public void run() {
try {
while (true) {
Thread.sleep(500);
String cake = "no." + nextId();
table.put(cake);
}

} catch (InterruptedException e) {
}
}

public synchronized int nextId() {
return id++;
}
}

//消费者代码
public class EaterThread extends Thread {
private final Table table;

public EaterThread(String name, Table table) {
super(name);
this.table = table;

}

public void run() {
try {
while (true) {
String cake = table.take();
Thread.sleep(1000);
}
} catch (InterruptedException e) {
}
}
}

//中间的桥梁
public class Table {
private final String [] buffer;
private int tail;
private int head;
private int count;

public Table(int count) {
this.buffer=new String [count];
this.head=0;
this.tail=0;
this.count=0;
}
//放不进的考虑
public synchronized void put(String cake) throws InterruptedException{
System.out.println(Thread.currentThread().getName()+" puts "+cake+" "+count);
while(count>=buffer.length){
wait();
}
buffer[tail]=cake;
tail=(tail+1)%buffer.length;
count++;
notifyAll();
}
//取不出的情况要有考虑
public synchronized String take() throws InterruptedException{
while(count<=0){
wait();
}
String cake=buffer[head];
head=(head+1)%buffer.length;
count--;
notifyAll();
System.out.println(Thread.currentThread().getName()+"take"+cake);
return cake;
}

}

最负责的部分就是对桥梁的封装设计，对与每一个线程的操作都要一致，如何保证的情况下，就是考虑两种情况的同时，保证只有一个线程修改临界区（感觉已经有read-write的一点共同点，但没有抓住关键点）。