JAVA中的ReentrantLock和ReentrantReadWriteLock锁简单使用

深藏阁楼爱情的钟 2022-03-25 11:00 203阅读 0赞

**ReentrantLock的作用和synchronize是一样的，都是实现锁的功能，但是ReentrantLock需要手写代码对锁进行获取和释放(一定要在finally里面释放)，要不然就永远死锁了，ReentrantLock也可以用来做线程之间的挂起和通知，synchronize一般是使用object的wait和notify来实现，ReentrantLock使用Condition来实现线程之间的通信。**

**ReentrantReadWriteLock锁是一个读写分离的锁，这种锁主要用于读多写少的业务场景，口诀就是：读读共享、谢谢互斥、读写互斥。**  
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#### ReentrantLock的简单使用 ####

private Lock lock = new ReentrantLock();  
lock.lock();用来获取锁。  
lock.unlock();用来释放锁

import java.util.concurrent.CopyOnWriteArrayList;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    public class UseReentrantLock {
    
        private Lock lock = new ReentrantLock();
    
        public void method1() {
            try {
                lock.lock();
                System.out.println("当前线程:" + Thread.currentThread().getName() + "进入method1..");
                Thread.sleep(1000);
                System.out.println("当前线程:" + Thread.currentThread().getName() + "退出method1..");
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                lock.unlock();
            }
        }
    
        public void method2() {
            try {
                lock.lock();
                System.out.println("当前线程:" + Thread.currentThread().getName() + "进入method2..");
                Thread.sleep(2000);
                System.out.println("当前线程:" + Thread.currentThread().getName() + "退出method2..");
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
    
                lock.unlock();
            }
        }
    
        public static void main(String[] args) {
    
            final UseReentrantLock ur = new UseReentrantLock();
            Thread t1 = new Thread(new Runnable() {
                @Override
                public void run() {
                    //ur.method1();
                    ur.method2();
                }
            }, "t1");
    
            t1.start();
            Thread t12 = new Thread(new Runnable() {
                @Override
                public void run() {
                    ur.method1();
                    //ur.method2();
                }
            }, "t12");
    
            t12.start();
            try {
                Thread.sleep(10);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            //System.out.println(ur.lock.getQueueLength());
        }
    
    
    }

#### ReentrantLock使用Condition的案例 ####

import java.util.concurrent.CopyOnWriteArrayList;
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    public class UseCondition {
    
    	private Lock lock = new ReentrantLock();
    	private Condition condition = lock.newCondition();
    	
    	public void method1(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" + Thread.currentThread().getName() + "进入等待状态..");
    			Thread.sleep(3000);
    			System.out.println("当前线程：" + Thread.currentThread().getName() + "释放锁..");
    			condition.await();	// Object wait
    			System.out.println("当前线程：" + Thread.currentThread().getName() +"继续执行...");
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public void method2(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" + Thread.currentThread().getName() + "进入..");
    			Thread.sleep(3000);
    			System.out.println("当前线程：" + Thread.currentThread().getName() + "发出唤醒..");
    			condition.signal();		//Object notify
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public static void main(String[] args) {
    		
    		final UseCondition uc = new UseCondition();
    		Thread t1 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				uc.method1();
    			}
    		}, "t1");
    		Thread t2 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				uc.method2();
    			}
    		}, "t2");
    		t1.start();
    
    		t2.start();
    	}
    	
    	
    	
    }

#### ReentrantLock使用多个Condition的案例 ####

package com.bjsxt.height.lock020;
    
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    
    public class UseManyCondition {
    
    	private ReentrantLock lock = new ReentrantLock();
    	private Condition c1 = lock.newCondition();
    	private Condition c2 = lock.newCondition();
    	
    	public void m1(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "进入方法m1等待..");
    			c1.await();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "方法m1继续..");
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public void m2(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "进入方法m2等待..");
    			c1.await();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "方法m2继续..");
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public void m3(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "进入方法m3等待..");
    			c2.await();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "方法m3继续..");
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public void m4(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "唤醒..");
    			c1.signalAll();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public void m5(){
    		try {
    			lock.lock();
    			System.out.println("当前线程：" +Thread.currentThread().getName() + "唤醒..");
    			c2.signal();
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			lock.unlock();
    		}
    	}
    	
    	public static void main(String[] args) {
    		
    		
    		final UseManyCondition umc = new UseManyCondition();
    		Thread t1 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				umc.m1();
    			}
    		},"t1");
    		Thread t2 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				umc.m2();
    			}
    		},"t2");
    		Thread t3 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				umc.m3();
    			}
    		},"t3");
    		Thread t4 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				umc.m4();
    			}
    		},"t4");
    		Thread t5 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				umc.m5();
    			}
    		},"t5");
    		
    		t1.start();	// c1
    		t2.start();	// c1
    		t3.start();	// c2
    		
    
    		try {
    			Thread.sleep(2000);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    
    		t4.start();	// c1
    		try {
    			Thread.sleep(2000);
    		} catch (InterruptedException e) {
    			e.printStackTrace();
    		}
    		t5.start();	// c2
    		
    	}
    	
    	
    	
    }

#### 其他的一下属性 ####

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#### ReentrantReadWriteLock的简单用法 ####

import java.util.concurrent.locks.ReentrantReadWriteLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock;
    import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;
    
    public class UseReentrantReadWriteLock {
    
    	private ReentrantReadWriteLock rwLock = new ReentrantReadWriteLock();
    	private ReadLock readLock = rwLock.readLock();
    	private WriteLock writeLock = rwLock.writeLock();
    	
    	public void read(){
    		try {
    			readLock.lock();
    			System.out.println("当前线程:" + Thread.currentThread().getName() + "进入...");
    			Thread.sleep(3000);
    			System.out.println("当前线程:" + Thread.currentThread().getName() + "退出...");
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			readLock.unlock();
    		}
    	}
    	
    	public void write(){
    		try {
    			writeLock.lock();
    			System.out.println("当前线程:" + Thread.currentThread().getName() + "进入...");
    			Thread.sleep(3000);
    			System.out.println("当前线程:" + Thread.currentThread().getName() + "退出...");
    		} catch (Exception e) {
    			e.printStackTrace();
    		} finally {
    			writeLock.unlock();
    		}
    	}
    	
    	public static void main(String[] args) {
    		
    		final UseReentrantReadWriteLock urrw = new UseReentrantReadWriteLock();
    		
    		Thread t1 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				urrw.read();
    			}
    		}, "t1");
    		Thread t2 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				urrw.read();
    			}
    		}, "t2");
    		Thread t3 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				urrw.write();
    			}
    		}, "t3");
    		Thread t4 = new Thread(new Runnable() {
    			@Override
    			public void run() {
    				urrw.write();
    			}
    		}, "t4");			
    //		t1.start();
    //		t2.start();
    //		t1.start(); // R 
    //		t3.start(); // W
    		t3.start();
    		t4.start();
    
    	}
    }

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