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分享2022-3-30作业
1、编写一个有两个线程的程序，第一个线程用来计算2～100000之间的素数的个数，第二个线程用来计算100000～200000之间的素数的个数，最后输出结果。
public class HWDemo01 {
public static void main(String[] args) throws InterruptedException {
Thread t1 = new Thread(){
@Override
public void run() {
for (int i = 2; i < 100000; i++) {
boolean flag = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
flag = false;
break;
}
}
if (flag) {
System.out.print(i + " ");
}
}
}
};
Thread t2 = new Thread(){
@Override
public void run() {
for (int i = 100000; i < 200000; i++) {
boolean flag = true;
for (int j = 2; j < i; j++) {
if (i % j == 0) {
flag = false;
break;
}
}
if (flag) {
System.out.print(i + " ");
}
}
}
};
t1.start();t2.start();
t1.join();t2.join();
}
}
2、模拟多线程并发问题，并解决（方式越多越好）
public class Account {
private int balance;//余额
public Account(int balance) {
this.balance = balance;
}
public int getBalance() {
return balance;
}
public void setBalance(int balance) {
this.balance = balance;
}
@Override
public String toString() {
return "Account{" +
"balance=" + balance +
'}';
}
}
方式1：public class AccountThread {
public static void main(String[] args) throws InterruptedException {
Account account = new Account(1000);
Thread t1 = new Thread(){
@Override
public void run() {
int balance = account.getBalance();
System.out.println("正在出钞...");
balance -= 200;
Thread.yield();//设置线程的状态 为 就绪状态
//修改余额
account.setBalance(balance);
System.out.println(Thread.currentThread().getName() +
"取了 200 余额：" + account.getBalance());
}
};
Thread t2 = new Thread(){
@Override
public void run() {
try {
t1.join();//写在t2线程的run中，会让t2等待t1运行结束之后再运行（串行）
int balance = account.getBalance();
System.out.println("正在出钞...");
balance -= 200;
Thread.yield();//设置线程的状态 为 就绪状态
//修改余额
account.setBalance(balance);
System.out.println(Thread.currentThread().getName() +
"取了 200 余额：" + account.getBalance());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
//让线程t1执行完毕取款操作后，再让线程t2执行即可，将线程的并发操作改为串行操作。
t1.start(); t2.start();
//下面两行代码 写在main线程中，会使得main线程去等待t1 t2的结束
t1.join(); t2.join();
System.out.println(Thread.currentThread().getName() + ":"+account.getBalance());
}
}
方式2：public class AccountThread02 {
public static void main(String[] args) throws InterruptedException {
Account account = new Account(1000);
Demo demo = new Demo();
Thread t1 = new Thread(){
@Override
public void run() {
synchronized (AccountThread02.class){
//需要保证原子性的代码 需要加锁的代码
int balance = account.getBalance();
System.out.println("正在出钞...");
balance -= 200;
Thread.yield();//设置线程的状态 为 就绪状态
//修改余额
account.setBalance(balance);
System.out.println(Thread.currentThread().getName() +
"取了 200 余额：" + account.getBalance());
}
}
};
Thread t2 = new Thread(){
@Override
public void run() {
synchronized (AccountThread02.class){
int balance = account.getBalance();
System.out.println("正在出钞...");
balance -= 200;
Thread.yield();//设置线程的状态 为 就绪状态
//修改余额
account.setBalance(balance);
System.out.println(Thread.currentThread().getName() +
"取了 200 余额：" + account.getBalance());
}
}
};
//让线程t1执行完毕取款操作后，再让线程t2执行即可，将线程的并发操作改为串行操作。
t1.start(); t2.start();
//下面两行代码 写在main线程中，会使得main线程去等待t1 t2的结束
t1.join(); t2.join();
System.out.println(Thread.currentThread().getName() + ":"+account.getBalance());
}
}
class Demo {}
方式3：public class SynchronizedDemo {
public static void main(String[] args) throws InterruptedException {
Account account = new Account(1000);
Demo demo = new Demo();
Thread t1 = new Thread() {
@Override
public void run() {
synchronized (account){
//需要保证原子性的代码 需要加锁的代码
int balance = account.getBalance();
System.out.println("正在出钞...");
balance -= 200;
Thread.yield();//设置线程的状态 为 就绪状态
//修改余额
account.setBalance(balance);
System.out.println(Thread.currentThread().getName() +
"取了 200 余额：" + account.getBalance());
}
}
};
Thread t2 = new Thread() {
@Override
public void run() {
synchronized (demo){
int balance = account.getBalance();
System.out.println("正在出钞...");
balance -= 200;
Thread.yield();//设置线程的状态 为 就绪状态
//修改余额
account.setBalance(balance);
System.out.println(Thread.currentThread().getName() +
"取了 200 余额：" + account.getBalance());
}
}
};
//让线程t1执行完毕取款操作后，再让线程t2执行即可，将线程的并发操作改为串行操作。
t1.start();
t2.start();
//下面两行代码 写在main线程中，会使得main线程去等待t1 t2的结束
t1.join();
t2.join();
System.out.println(Thread.currentThread().getName() + ":" + account.getBalance());
}
}
3.模拟两个人(两个线程)，同时在桌子上拿豆子，考虑并发出错情况
public class Beans {
private int num ;
public Beans(int num) {
this.num = num;
}
public void catchBeans() {
if (num == 0){
throw new RuntimeException("豆子没了");
}
int n = num;
n = n - 1;
Thread.yield();
num = n;
}
public int getNum() {
return num;
}
public void setNum(int num) {
this.num = num;
}
}
public class BeansTest {
public static void main(String[] args) {
Beans beans = new Beans(100);
Thread t1 = new Thread() {
@Override
public void run() {
while (true) {
beans.catchBeans();
Thread.yield();
System.out.println(beans.getNum());
}
}
};
Thread t2 = new Thread() {
@Override
public void run() {
while (true) {
beans.catchBeans();
Thread.yield();
System.out.println(beans.getNum());
}
}
};
t1.start();
t2.start();
}
}
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