• Java马士兵高并发编程视频学习笔记(二)


    1.ReentrantLock的简单使用  

    Reentrant n.再进入

    ReentrantLock 一个可重入互斥Lock具有与使用synchronized方法和语句访问的隐式监视锁相同的基本行为和语义,但具有扩展功能。(从jdk1.8中文版复制而来)

    可以完成synchronized相同的作用,但必须手动释放锁

    复制代码
    package com.dingyu2;
    

    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;

    /**

    • Reentrant n.再进入
    • ReentrantLock 一个可重入互斥Lock具有与使用synchronized方法和语句访问的隐式监视锁相同的基本行为和语义,但具有扩展功能。(从jdk1.8中文版复制而来)
    • 可以完成synchronized相同的作用,但必须手动释放锁
    • @author dingyu

    */
    public class ReentrantLock1 {
    private Lock lock = new ReentrantLock();

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m1() {
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            lock.lock();//synchronized(this)类似,锁定的是堆的对象
            </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i &lt; 10; i++<span style="color: #000000;">)
                System.out.println(</span>"m1-" +<span style="color: #000000;"> i);
        } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (Exception e) {
            System.out.println(</span>"m1启动"<span style="color: #000000;">);
    
        } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
            System.out.println(</span>"m1结束"<span style="color: #000000;">);
            lock.unlock();
        }
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m2() {
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            lock.lock();
            </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i &lt; 10; i++<span style="color: #000000;">)
                System.out.println(</span>"m2-" +<span style="color: #000000;"> i);
    
        } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (Exception e) {
            System.out.println(</span>"m2启动"<span style="color: #000000;">);
    
        } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
            System.out.println(</span>"m2结束"<span style="color: #000000;">);
            lock.unlock();
        }
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
        ReentrantLock1 reentrantLock1 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> ReentrantLock1();
        </span><span style="color: #0000ff;">new</span> Thread(() -&gt;<span style="color: #000000;"> reentrantLock1.m1()).start();
        </span><span style="color: #0000ff;">new</span> Thread(() -&gt;<span style="color: #000000;"> reentrantLock1.m2()).start();
    }
    

    }

    复制代码

    2.ReentrantLock对synchronized的扩展之tryLock()

    复制代码
    package com.dingyu2;
    

    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;

    /**

    • ReentrantLock对synchronized的扩展之tryLock()
    • @author dingyu

    */
    public class ReentrantLock2 {
    private Lock lock = new ReentrantLock();

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m1() {
        lock.lock();</span><span style="color: #008000;">//</span><span style="color: #008000;"> 一直锁着,不手动释放, 和synchronized(this)类似,锁定的是堆的对象</span>
    

    }

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m2() {
        </span><span style="color: #0000ff;">boolean</span> isNotLock = lock.tryLock();<span style="color: #008000;">//</span><span style="color: #008000;"> 如果别的进程锁着就返回false,如果没锁返回true
        </span><span style="color: #008000;">//</span><span style="color: #008000;"> 我们可以根据有没有锁来执行自己的逻辑,而不需要等着锁的释放,更加灵活</span>
        <span style="color: #0000ff;">if</span><span style="color: #000000;"> (isNotLock) {
            System.out.println(</span>"lock对象没有被锁定"<span style="color: #000000;">);
        } </span><span style="color: #0000ff;">else</span><span style="color: #000000;"> {
            System.out.println(</span>"lock对象被锁定了"<span style="color: #000000;">);
        }
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
        ReentrantLock2 reentrantLock2 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> ReentrantLock2();
        </span><span style="color: #0000ff;">new</span> Thread(() -&gt;<span style="color: #000000;"> reentrantLock2.m1()).start();
        </span><span style="color: #0000ff;">new</span> Thread(() -&gt;<span style="color: #000000;"> reentrantLock2.m2()).start();
    }
    

    }

    复制代码

    3.ReentranLock对synchronized的扩展:可以被另外的线程打断

    复制代码
    package com.dingyu2;
    

    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;

    /**

    • ReentranLock对synchronized的扩展:可以被另外的线程打断
    • 因为m1方法一直占着锁,m2永远不可能得到锁,既然得不到锁,我们就关闭m2好了,这时候得用lockInterruptibly
    • @author dingyu

    */
    public class ReentrantLock3 {
    private Lock lock = new ReentrantLock();

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m1() {
        lock.lock();
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            System.out.println(</span>"t1 start"<span style="color: #000000;">);
            </span><span style="color: #0000ff;">while</span> (<span style="color: #0000ff;">true</span><span style="color: #000000;">) {
            }
        } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
            lock.unlock();
            System.out.println(</span>"t1 end"<span style="color: #000000;">);
        }
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m2() {
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            lock.lockInterruptibly();
            System.out.println(</span>"t2 start"<span style="color: #000000;">);
        } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) {
            System.out.println(</span>"t2被打断了"<span style="color: #000000;">);
        } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
            </span><span style="color: #0000ff;">if</span><span style="color: #000000;"> (lock.tryLock())
                lock.unlock();
            System.out.println(</span>"t2 end"<span style="color: #000000;">);
        }
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
        ReentrantLock3 reentrantLock3 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> ReentrantLock3();
        Thread t1 </span>= <span style="color: #0000ff;">new</span> Thread(() -&gt; reentrantLock3.m1(), "t1"<span style="color: #000000;">);
        t1.start();
        Thread t2 </span>= <span style="color: #0000ff;">new</span> Thread(() -&gt; reentrantLock3.m2(), "t2"<span style="color: #000000;">);
        t2.start();
        t2.interrupt();
    }
    

    }

    复制代码

    4.ReentrantLock对synchronized的扩展 : 可以指定公平锁

    复制代码
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;
    

    /**

    • ReentrantLock对synchronized的扩展 : 可以指定公平锁,哪个线程等待时间长,哪个先执行
    • 在构造函数中放入ture参数
    • @author dingyu

    */
    public class ReentrantLock4 {
    private Lock lock = new ReentrantLock(true);

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m1() {
        </span><span style="color: #0000ff;">for</span> (<span style="color: #0000ff;">int</span> i = 0; i &lt; 10; i++<span style="color: #000000;">) {
            </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                lock.lock();
                System.out.println(Thread.currentThread().getName() </span>+ "running"<span style="color: #000000;">);
            } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
                lock.unlock();
            }
        }
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
        ReentrantLock4 lock4 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> ReentrantLock4();
        </span><span style="color: #0000ff;">new</span> Thread(()-&gt;lock4.m1(),"t1"<span style="color: #000000;">).start();
        </span><span style="color: #0000ff;">new</span> Thread(()-&gt;lock4.m1(),"t2"<span style="color: #000000;">).start();
    }
    

    }

    复制代码

    5.使用wait和notifyAll实现消费者生产者模式

    复制代码
    package com.dingyu2;
    

    import java.util.LinkedList;

    /**

    • 使用wait和notifyAll实现消费者生产者模式
    • @author dingyu

    */
    public class ProduceConsumer {
    private final LinkedList<Integer> lists = new LinkedList<Integer>();
    private final int MAX = 10;
    private int count = 0;

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">synchronized</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> put(Integer i) {
        </span><span style="color: #0000ff;">while</span> (lists.size() == MAX) { <span style="color: #008000;">//</span><span style="color: #008000;"> wait大多数情况和while一起用</span>
            <span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                </span><span style="color: #0000ff;">this</span>.wait();<span style="color: #008000;">//</span><span style="color: #008000;"> 如果满了我就释放锁,并且等待</span>
            } <span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) {
                e.printStackTrace();
            }
        }
        lists.add(i);</span><span style="color: #008000;">//</span><span style="color: #008000;"> 生产一个</span>
        count++<span style="color: #000000;">;
        </span><span style="color: #0000ff;">this</span>.notifyAll();<span style="color: #008000;">//</span><span style="color: #008000;"> 叫醒消费者可以消费啦</span>
    

    }

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">synchronized</span><span style="color: #000000;"> Integer get() {
        </span><span style="color: #0000ff;">while</span> (lists.size() == 0<span style="color: #000000;">) {
            </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                </span><span style="color: #0000ff;">this</span>.wait();<span style="color: #008000;">//</span><span style="color: #008000;"> 如果集合为空,不能消费,释放锁,等着</span>
            } <span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) {
                e.printStackTrace();
            }
        }
        Integer num </span>=<span style="color: #000000;"> lists.removeFirst();
        count</span>--<span style="color: #000000;">;
        </span><span style="color: #0000ff;">this</span>.notifyAll();<span style="color: #008000;">//</span><span style="color: #008000;"> 叫醒生产者,可以继续生产啦</span>
        <span style="color: #0000ff;">return</span><span style="color: #000000;"> num;
    }
    

    }

    复制代码

    6.使用Condition 完成生产者消费者模式

    复制代码
    package com.dingyu2;
    /**
     * 使用Condition 完成生产者消费者模式
     * @author dingyu
     *
     */
    

    import java.util.LinkedList;
    import java.util.concurrent.locks.Condition;
    import java.util.concurrent.locks.Lock;
    import java.util.concurrent.locks.ReentrantLock;

    public class ProduceConsumer2 {
    private final LinkedList<Integer> lists = new LinkedList<Integer>();
    private final int MAX = 10;
    private int count = 0;

    </span><span style="color: #0000ff;">private</span> Lock lock = <span style="color: #0000ff;">new</span><span style="color: #000000;"> ReentrantLock();
    </span><span style="color: #0000ff;">private</span> Condition p = lock.newCondition();<span style="color: #008000;">//</span><span style="color: #008000;"> 生产者</span>
    <span style="color: #0000ff;">private</span> Condition c = lock.newCondition();<span style="color: #008000;">//</span><span style="color: #008000;"> 消费者</span>
    
    <span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> put(Integer i) {
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            lock.lock();
            </span><span style="color: #0000ff;">while</span> (lists.size() ==<span style="color: #000000;"> MAX) {
                </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                    p.await();
                } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            lists.add(i);
            count</span>++<span style="color: #000000;">;
            c.signalAll();
        } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
            lock.unlock();
        }
    }
    
    </span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Integer get() {
        Integer i </span>= <span style="color: #0000ff;">null</span><span style="color: #000000;">;
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            lock.lock();
            </span><span style="color: #0000ff;">while</span> (lists.size() == 0<span style="color: #000000;">) {
                </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
                    c.await();
                } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            i </span>=<span style="color: #000000;"> lists.removeFirst();
            count</span>++<span style="color: #000000;">;
            p.signalAll();
        } </span><span style="color: #0000ff;">finally</span><span style="color: #000000;"> {
            lock.unlock();
        }
        </span><span style="color: #0000ff;">return</span><span style="color: #000000;"> i;
    }
    

    }

    复制代码

     7.ThreadLocal 线程局部变量  每个线程中的这个变量归自己线程管

    复制代码
    package com.dingyu;
    

    public class ThreadLocal1 {
    private ThreadLocal<Integer> tl = new ThreadLocal<Integer>();

    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m1() {
        System.out.println(tl.get());
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> m2() {
        tl.set(</span>7898<span style="color: #000000;">);
    }
    
    </span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">static</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> main(String[] args) {
        ThreadLocal1 local1 </span>= <span style="color: #0000ff;">new</span><span style="color: #000000;"> ThreadLocal1();
        </span><span style="color: #0000ff;">new</span> Thread(() -&gt;<span style="color: #000000;"> local1.m2()).start();
    
        </span><span style="color: #0000ff;">try</span><span style="color: #000000;"> {
            Thread.sleep(</span>5000<span style="color: #000000;">);
        } </span><span style="color: #0000ff;">catch</span><span style="color: #000000;"> (InterruptedException e) {
            e.printStackTrace();
        }
    
        </span><span style="color: #0000ff;">new</span> Thread(() -&gt;<span style="color: #000000;"> local1.m1()).start();
    }
    

    }

    复制代码
    原文地址:https://www.cnblogs.com/dddyyy/p/9975838.html
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  • 原文地址:https://www.cnblogs.com/jpfss/p/10991714.html
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