Black Horse programmer _java Multithreading single case design

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I. Threading Methods

• 1.yield yield CPU
• 2.setPriority () Sets the priority of the thread

Two. Single Case design mode

• Singleton design Pattern: guarantees that the class has only one object in memory.

• How do you ensure that the class has only one object in memory?

  • (1) control the creation of classes, and do not allow other classes to create objects of this class. Private
  • (2) Define an object of this class in this class. Singleton s;
  • (3) to provide public access. public static Singleton getinstance () {return s}

• There are two types of single-case notation:

  • (1) A Hungry man-type development in this way.

  • //饿汉式class Singleton {    //1,私有构造函数    private Singleton(){}    //2,创建本类对象    private static Singleton s = new Singleton();    //3,对外提供公共的访问方法    public static Singleton getInstance() {        return s;    }    public static void print() {        System.out.println("11111111111");    }}

  • (2) Lazy-type interview to write this way. Multi-threaded problem?

  • //懒汉式,单例的延迟加载模式class Singleton {    //1,私有构造函数    private Singleton(){}    //2,创建本类对象    private static Singleton s;    //3,对外提供公共的访问方法    public static Singleton getInstance() {        if(s == null)            //线程1,线程2            s = new Singleton();        return s;    }    public static void print() {        System.out.println("11111111111");    }}

  • (3) Third form

  • class Singleton {    private Singleton() {}    public static final Singleton s = new Singleton();//final是最终的意思,被final修饰的变量不可以被更改}

  • The runtime class is a singleton class

  • Runtime r = Runtime.getRuntime();//r.exec("shutdown -s -t 300");     //300秒后关机r.exec("shutdown -a");              //取消关机

  • Timer class: Timer

    public class Demo5_Timer {    /**     * @param args     * 计时器     * @throws InterruptedException      */    public static void main(String[] args) throws InterruptedException {        Timer t = new Timer();        t.schedule(new MyTimerTask(), new Date(114,9,15,10,54,20),3000);        while(true) {            System.out.println(new Date());            Thread.sleep(1000);        }    }}class MyTimerTask extends TimerTask {    @Override    public void run() {        System.out.println("起床背英语单词");    }}

Three. Communication between threads

• 1. When to communicate
  • When multiple threads are executing concurrently, the CPU is randomly switching threads by default
  • If we want them to execute regularly, we can use communication, for example, each thread performs a print
• 2. How to Communicate
  • Call Wait () if you want the thread to wait
  • If you want to wake up the waiting thread, call notify ();
  • Both methods must be executed in the synchronization code, and the synchronization lock object is used to invoke the
• 3. Issues with multiple thread communication
  • The Notify () method is a random wake-up of a thread
  • The Notifyall () method is to wake all threads
  • JDK5 Unable to wake a specified thread before
  • If the communication between multiple threads, you need to use Notifyall () to notify all threads, use while to repeatedly judge the condition

Four. After JDK5, the line program control system

• 1. Synchronization
  • Synchronizing using the Lock () and Unlock () Methods of the Reentrantlock class
• 2. Communication
  • Use the Newcondition () method of the Reentrantlock class to get the condition object
  • Use condition's await () method when you need to wait, wake up with the signal () method
  • Different threads use different condition so that you can tell which thread to look for when waking up.

Five. Summary of synchronous and non-synchronous classes

• StringBuffer and Stringbuilder,stringbuffer are thread-safe, inefficient, StringBuilder are thread insecure, high efficiency
• Vectors and Arraylist,vector are thread-safe, inefficient, ArrayList are thread insecure and highly efficient
• Hashtable and hashmap,hashtable are thread-safe, inefficient, hashmap are thread insecure, high efficiency

Black Horse programmer _java Multithreading single case design