一种不安全的写法
public class Main {public static final Object lock1 = new Object();public static final Object lock2 = new Object();public static void main(String[] args) {Thread thread1 = new Thread(new Runnable() {@Overridepublic void run() {synchronized (lock1) {System.out.println(Thread.currentThread().getName() + "已经获取了lock1");try {Thread.sleep(100);} catch (InterruptedException e) {throw new RuntimeException(e);}synchronized (lock2) {System.out.println(Thread.currentThread().getName() + "已经获取了lock2");}}}});Thread thread2 = new Thread(new Runnable() {@Overridepublic void run() {synchronized (lock2) {System.out.println(Thread.currentThread().getName() + "已经获取了lock2");try {Thread.sleep(100);} catch (InterruptedException e) {throw new RuntimeException(e);}synchronized (lock1) {System.out.println(Thread.currentThread().getName() + "已经获取了lock1");}}}});thread1.start();thread2.start();}
}
一种安全的写法
import java.io.*;
import java.sql.Time;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
import java.util.stream.Collectors;public class Main {public static final ReentrantLock lock1 = new ReentrantLock();public static final ReentrantLock lock2 = new ReentrantLock();public static void main(String[] args) {Thread thread1 = new Thread(new Runnable() {@Overridepublic void run() {try {// 尝试获取 lock1,等待2秒if (lock1.tryLock(2, TimeUnit.SECONDS)) {try {System.out.println("Thread1: Holding lock1...");// 尝试获取 lock2,等待2秒if (lock2.tryLock(2, TimeUnit.SECONDS)) {try {System.out.println("Thread1: Holding lock1 & lock2...");// Critical section} finally {lock2.unlock();}} else {System.out.println("Thread1: Could not acquire lock2, releasing lock1...");}} finally {lock1.unlock();System.out.println("Thread1: releasing lock1...");}} else {System.out.println("Thread1: Could not acquire lock1...");}} catch (InterruptedException e) {e.printStackTrace();}}});Thread thread2 = new Thread(new Runnable() {@Overridepublic void run() {try {// 尝试获取 lock2,等待2秒if (lock2.tryLock(2, TimeUnit.SECONDS)) {try {System.out.println("Thread2: Holding lock2...");// 尝试获取 lock1,等待2秒if (lock1.tryLock(2, TimeUnit.SECONDS)) {try {System.out.println("Thread2: Holding lock2 & lock1...");// Critical section} finally {lock1.unlock();}} else {System.out.println("Thread2: Could not acquire lock1, releasing lock2...");}} finally {lock2.unlock();System.out.println("Thread2: releasing lock2...");}} else {System.out.println("Thread2: Could not acquire lock2...");}} catch (InterruptedException e) {e.printStackTrace();}}});thread1.start();thread2.start();}
}