8.（线程同步）有下面代码
class MyThread extends Thread{
private String data;
public MyThread(String data){
this.data = data;
}
public void run(){
for(int i = 0; i<100; i++){
System.out.println(data);
}
}
}
public class TestMyThread{
public static void main(String args[]){
Thread t1 = new MyThread(“aaa”);
Thread t2 = new MyThread(“bbb”);
t1.start();
t2.start();
}
}
现希望能够同步的输出 aaa 和 bbb，即一次输出 100 个 aaa 或 bbb，输出这两个字符串时没有交互。为了达到上述目的，要对原代码进行修改。以下哪些修改方式能够得到想要的结果？ AC
A.把第 6 行改为 public synchronized void run()
B.把 run 方法中所有的内容都放在 synchronized(data)代码块中
C.把 run 方法中所有的内容都放在 synchronized(System.out)代码块中
9.（线程综合）代码改错
class MyThread1 implements
Runnable{ public void run() {
for(int i = 0; i<100;
i++){ this.sleep((int)(Math.random()*1000));
System.out.println(“hello”);
}
}
}
class MyThread2 extends Thread{ public void run() throws Exception {
for(int i = 0; i<100; i++){
this.sleep((int)(Math.random()*1000));
System.out.println(“world”);
}
}
}
public class TestMyThread{
public static void main(String args[]){
Runnable t1 = new MyThread1();
Thread t2 = new MyThread2();
t1.start();
t2.start();
}
}
class MyThread9 implements Runnable{
@Override
public void run() {
// TODO Auto-generated method stub
for(int i=0;i<100;i++) {
try {
Thread.sleep((int)(Math.random()*1000));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("hello");
}
}
}
class MyThread10 implements Runnable{
@Override
public void run(){
// TODO Auto-generated method stub
for(int i=0;i<100;i++) {
try {
Thread.sleep((int)(Math.random()*1000));
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("world");
}
}
}
public class Test9 {
public static void main(String[] args) {
// TODO Auto-generated method stub
Runnable t1=new MyThread9();
Thread t3=new Thread(t1);
Thread t2=new Thread (new MyThread10());
t3.start();
t2.start();
}
消费生产问题
public class TestProductCustomer {
public static void main(String[] args) {
Shop shop = new Shop();//共享资源对象
Thread p = new Thread(new Product(shop),"生产者");
Thread c = new Thread(new Customer(shop),"消费者");
p.start();
c.start();
}
}
class Goods{
private int id;
public Goods(int id) {
this.id = id;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
}
class Shop{
Goods goods;
boolean flag;//标识商品是否充足
//生产者调用的 存的方法
public synchronized void saveGoods(Goods goods) throws InterruptedException {
//1.判断商品是否充足
if(flag == true) {
System.out.println("生产者：商品充足！要等待了！");
this.wait();//商品充足，生产者不用生产，而等待消费者买完！进入等待状态
}
//商品不充足！生产者生产商品，存到商场里
System.out.println(Thread.currentThread().getName()+"生产并在商场里存放了"+goods.getId()+"件商品");
this.goods = goods;
flag = true;//已经有商品了！可以让消费者购买了！
//消费者等待。。。
this.notifyAll();//将等待队列的消费者唤醒！前来购买商品
}
//消费者调用的 取的方法
public synchronized void buyGoods() throws InterruptedException {
if(flag == false) {//没有商品了！消费者就要等待！
System.out.println("消费者：商品不充足！要等待了！");
this.wait();//消费者进入等待队列！等待生产者生产商品后，唤醒！
}
//正常购买商品
System.out.println(Thread.currentThread().getName()+"购买了"+goods.getId()+"件商品");
//商品买完了！标识没货了！
this.goods = null;
flag =false;
//唤醒生产者去生产商品
this.notifyAll();
}
}
//生产者
class Product implements Runnable{
Shop shop;//商场
public Product(Shop shop) {
this.shop = shop;
}
public void run() {
//通过循环，生产商品存放到Shop里
for(int i = 1;i<=30;i++) {
try {
//生产者线程调用存商品的方法。传一个商品对象
this.shop.saveGoods(new Goods(i));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
//消费者
class Customer implements Runnable{
Shop shop;//商场
public Customer(Shop shop) {
this.shop = shop;
}
public void run() {
for(int i =1;i<=30;i++) {
try {
this.shop.buyGoods();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
