class bread{
int num = 0;
public synchronized void makeBreand(){
num++;
this.notify();
}
public synchronized void sale(){
while(num==0){
try{
this.wait();
System.out.println("暂时无面包，等待");
}catch(InterruptedException e){e.printStackTrace();}
}
num--;
}
}
class makeThread implements Runnable{
bread account;
public makeThread(bread s){
account = s;
}
public void run(){
while(account.num<10){
account.makeBreand();
System.out.println(Thread.currentThread().getName()+"thread is working");
System.out.println("面包数量+1,已有"+account.num+"个面包");
try{
Thread.sleep(1000);
}catch(InterruptedException e){e.printStackTrace();}
}
}
}
class saleThread implements Runnable{
bread left;
public saleThread(bread s){
left = s;
}
public void run(){
if(left.num>0){
left.sale();
System.out.println(Thread.currentThread().getName()+"售出面包一个");
System.out.println("目前有"+left.num+"个面包");
try{
Thread.sleep(1000);
}catch(InterruptedException e){e.printStackTrace();}
}
}
}
public class test{
public static void main(String[] args){
bread b = new bread();
saleThread sale = new saleThread(b);
makeThread make = new makeThread(b);
Thread t1 = new Thread(make);
Thread t2 = new Thread(sale);
t1.start();
t2.start();
}
}
代码如下，运行效果：
Thread-1售出面包一个
Thread-0thread is working
目前有0个面包
面包数量+1,已有0个面包
Thread-0thread is working
面包数量+1,已有1个面包
Thread-0thread is working
面包数量+1,已有2个面包
Thread-0thread is working
面包数量+1,已有3个面包
Thread-0thread is working
面包数量+1,已有4个面包
Thread-0thread is working
面包数量+1,已有5个面包
Thread-0thread is working
面包数量+1,已有6个面包
Thread-0thread is working
面包数量+1,已有7个面包
Thread-0thread is working
面包数量+1,已有8个面包
Thread-0thread is working
面包数量+1,已有9个面包
Thread-0thread is working
面包数量+1,已有10个面包
为什么我的sale进程只被调用了一次？
首先，sale操作是在线程1中执行的，因为第一个线程t1 先启动了，导致num很快就非0类，那么sale操作的while循环就结束了。
其次，你的一个操作中的打印语句应该放在同一条，因为是多线程环境下，比如你的sale操作中前后两条打印语句可能就是错乱的，不是同时出现的。修正下你的打印语句，就知道为什么了。
class bread {
int num = 0;
public synchronized void makeBreand() {
num++;
this.notify();
}
public synchronized void sale() {
System.out.println(Thread.currentThread().getName()+" num:"+num);
while (num == 0) {
try {
System.out.println("暂时无面包，等待");
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
num--;
}
}
class makeThread implements Runnable {
bread account;
public makeThread(bread s) {
account = s;
}
public void run() {
while (account.num < 10) {
account.makeBreand();
System.out.println(Thread.currentThread().getName() + "thread is working"+"面包数量+1,已有" + account.num + "个面包");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class saleThread implements Runnable {
bread left;
public saleThread(bread s) {
left = s;
}
public void run() {
if (left.num > 0) {
left.sale();
System.out.println(Thread.currentThread().getName() + "售出面包一个"+"目前有" + left.num + "个面包");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class bread {
int num = 0;
public synchronized void makeBreand() {
num++;
this.notify();
}
public synchronized void sale() {
while (num <= 0) {
try {
System.out.println("暂时无面包，等待");
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
num--;
}
}
class makeThread implements Runnable {
bread account;
public makeThread(bread s) {
account = s;
}
public void run() {
while (account.num < 10) {
account.makeBreand();
System.out.println("面包数量+1,已有" + account.num + "个面包");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class saleThread implements Runnable {
bread left;
public saleThread(bread s) {
left = s;
}
public void run() {
if (left.num > 0) {
left.sale();
System.out.println("售出面包一个 目前有" + left.num + "个面包");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
这个很显然，你的saleThread线程的run方法没有循环条件，里面的逻辑只会执行一次。
可能有些时候一次都不执行，这是因为saleThread可能会先于makeThread执行，此时left.num==0，run方法就结束了。
还有，bread的sale方法里面的while语句很奇怪，这个地方使用while与if有什么区别么？
还有，为什么类名都是小写的……
循环条件不对，应该用结束标志的