經典例題:生產者/消費者問題
生產者(Productor)將產品交給店員(Clerk),而消費者(Customer)從店員處取走產品,
店員一次只能持有固定數量的產品(比如:20),如果生產者試圖生產更多的產品,店員
會叫生產者停一下,如果店中有空位放產品了再通知生產者繼續生產;如果店中沒有產品
了,店員會告訴消費者等一下,如果店中有產品了再通知消費者來取走產品。
class Clerk{
private int productCount = 0;
/**
* 生產產品
*/
public synchronized void produceProduct() {
if(productCount < 20){
productCount++;
System.out.println(Thread.currentThread().getName() + ":開始生產第" + productCount + "個產品!");
notify();
}else{
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
/**
* 消費產品
*/
public synchronized void consumeProduct() {
if(productCount > 0){
System.out.println(Thread.currentThread().getName() + ":開始消費第" + productCount + "個產品!");
productCount--;
notify();
}else{
try {
wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class Producer extends Thread{
private Clerk clerk;
public Producer(Clerk clerk) {
this.clerk = clerk;
}
@Override
public void run() {
System.out.println(getName() + ":開始生產產品.....");
while(true){
try {
Thread.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
clerk.produceProduct();
}
}
}
class Consumer extends Thread{
private Clerk clerk;
public Consumer(Clerk clerk) {
this.clerk = clerk;
}
@Override
public void run() {
System.out.println(getName() + ":開始消費產品.....");
while(true){
try {
Thread.sleep(20);
} catch (InterruptedException e) {
e.printStackTrace();
}
clerk.consumeProduct();
}
}
}
public class ProductTest {
public static void main(String[] args) {
Clerk clerk = new Clerk();
Producer p1 = new Producer(clerk);
p1.setName("生產者1");
Consumer c1 = new Consumer(clerk);
c1.setName("消費者1");
Consumer c2 = new Consumer(clerk);
c2.setName("消費者2");
p1.start();
c1.start();
c2.start();
}
}
問題2:關於lock鎖的使用方法,應該使用try-finally代碼塊
public void test(double amt){
try {
lock.lock();
System.out.println("同步內容...");
}finally {
lock.unlock();
}
}