Dark Horse Programmer--multi-threaded synchronization of a layer of objects/two-layer objects/three-layer object comparison

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Objective:

In object-oriented thinking, the threading method can be divided into three types according to the level of the object to be created:

1, a layer of object writing: the use of extends thread, the replication of the parent class of the run () method, directly establish a thread instance object, this method is simple, suitable for single-task one-way requirements. Do not have much discussion here;

2, two-level object writing: Using the implements Runnable interface, the copy interface of the Run () method to get two levels of objects-often called task objects, and then by passing the two-level object into the (responsible for the main () method) of the first class object of the new Thread () construction parameters, The first-level object takes the polymorphic thread reference to the run () method;

Import java.util.random;//Two threads example of buying a ticket: Class FinalDemo1 implements Runnable {private int[] arr = new Int[6];p rivate int n=0 ;//private int num = 50;public void run () {for (int i = 0; i <, i++) {synchronized (this) {if (/*num > 0 && ; */n<6) {try {Thread.Sleep]} catch (Interruptedexception e) {e.printstacktrace ();} System.out.println (Thread.CurrentThread (). GetName () + "sold the first"//+ num--+ "Ticket! arr[n]= new Random (). Nextint (), n++;for (int a:arr) {System.out.print (a);}                    System.out.println ();}}}} public class MyThreadDemo2 {public static void main (string[] args) {FinalDemo1 f = new FinalDemo1 (); New Thread (F, "A"). STA RT (); New Thread (F, "B"). Start (); new Thread (F, "C"). Start ();}}

Two-layer notation Note: Shared resources are generally written on private properties, so when you create a thread, you cannot new multiple runnable! Otherwise, multithreading performs many of the same tasks; You should first new a Runnable object R and always pass this object to multiple new Thread (R).

3, three layers of object writing: On the basis of the two-layer notation, because of the complexity of the task, the establishment of a third object-often called the resource resource object to be responsible for the establishment of different processing methods, common is a production method, a consumer method, or to alternate execution of two other methods;

Because resources are unique, there are attributes to be shared, so more rigorous can be written as Singleton, so that the new thread (new Runnable (RES)) forms a three-tier object to complete a thread definition, and multiple threads of multiple tasks work together with a res to ensure security, Just synchronize the methods in Res.

Give two examples:

An example of a task, multiple threads: Although you can use the two-level object notation, but after extracting the third layer of resource objects, you can better control the thread task, such as alternating execution;

Two threads populate an array problem: Import Java.util.random;public class Test {/* * declares a shared array, two threads, two threads separated for a period of time (can write a random number),         * Add data to the array, and each thread will add 3 data to the group. * */public static void main (string[] args) {final Sharearr Sharearr = Sha                                Rearr.getinstance ();                                New Thread (New Runnable () {public void run () { for (int i = 0;i<3;i++) {Sharea                                Rr.addnumfirst ();                                }}). Start ();                Because a level three design is used, the same object is called on the resource, so different methods still share the private property, so the "i+1" elements of the two threads can be synchronized;                                New Thread (New Runnable () {public void run () {     for (int i = 0;i<3;i++) {                                   Sharearr.addnumsecond ();        }}). Start ();        }}class Sharearr {Private Sharearr () {};        private static Sharearr arr = null; public static Sharearr getinstance () {if (arr = = null) {synch                                Ronized (Sharearr.class) {if (arr = = null)                                {arr = new Sharearr ();        }}} return arr;        } private int[] array = new INT[6];        private int i = 0;        Boolean flag = true;                                Public synchronized void Addnumfirst () {while (!flag) {try {                        This.wait (); } catch (InterruptedexceptiOn e) {e.printstacktrace ();                }} try {thread.sleep (1000);                } catch (Interruptedexception e) {e.printstacktrace ();                } int num = new Random (). Nextint ();                System.out.println (Thread.CurrentThread (). GetName () + "Assign value to array" + (i+1) + "element" +num);                array[i++] = num;                Flag = false;        This.notify ();                        } public synchronized void Addnumsecond () {while (flag) {                        try {this.wait ();                        } catch (Interruptedexception e) {e.printstacktrace ();                }} try {thread.sleep (1000); } catch (Interruptedexception e) {e.printstAcktrace ();                } int num = new Random (). Nextint ();                System.out.println (Thread.CurrentThread (). GetName () + "Assign value to array" + (i+1) + "element" +num);                array[i++] = num;                Flag = true;        This.notify (); }}

Multi-tasking, multi-threaded example: generally have to use three-layer object writing;

Example of synchronized and lock mode for production & consumption: Producerconsumerdemoclass producerconsumerdemo2{public static void Main (string[] args) {Resource r=new Resource (); Producer pro=new Producer (R); Consumer con=new Consumer (R); Thread T1=new thread (PRO); Thread T2=new thread (PRO); Thread t3=new thread (con); Thread t4=new thread (con); T1.start (); T2.start (); T3.start (); T4.start (); System.out.println ("Hello world!");}} Class Resource {private string name;private int count=1;private boolean flag=false;public synchronized void set (String nam e) {while (flag) try{wait ();} catch (Exception e) {}this.name=name+ "--" +count++; System.out.println (Thread.CurrentThread (). GetName () + "... Producer ... "+this.name); Flag=true;this.notifyall ();} Public synchronized void out () {while (!flag) try{wait ();} catch (Exception e) {}system.out.println (Thread.CurrentThread (). GetName () + "... Consumer ... "+this.name); Flag=false;this.notifyall ();}} Class Producer implements Runnable{private Resource Res; Producer (Resource res) {this.res=res;} public void Run () {while (true) {Res.set ("+ goods +");}}} Class Consumer implements Runnable{private Resource Res; Consumer (Resource res) {this.res=res;} public void Run () {while (true) {Res.out ()}}} Import Java.util.concurrent.locks.*;class producerconsumerdemo2{public static void Main (string[] args) {Resource r=new Resource (); Producer pro=new Producer (R); Consumer con=new Consumer (R); Thread T1=new thread (PRO); Thread T2=new thread (PRO); Thread t3=new thread (con); Thread t4=new thread (con); T1.start (); T2.start (); T3.start (); T4.start (); System.out.println ("Hello world!");}} Class Resource {private String name;private int count=1;private boolean flag=false;private Lock lock=new reentrantlock (); Interface class private Condition condition_pro=lock.newcondition ();p rivate Condition condition_con=lock.newcondition (); public void Set (String name) throws interruptedexception//Interrupt exception {lock.lock (); Try{while (flag) condition_pro.await ();// Condition wait method, stop pro thread. this.name=name+ "--" +count++; System.out.println (Thread.CurrentThread (). GetName () + "... Producer ... "+thIs.name); flag=true;condition_con.signal ();} Finally{lock.unlock ();}} public void Out () throws Interruptedexception{lock.lock (); Try{while (!flag) condition_con.await ();//try{wait ();} catch (Exception e) {}system.out.println (Thread.CurrentThread (). GetName () + "... Consumer ... "+this.name); flag=false;condition_pro.signal ();//this.notifyall (); wake-up All}finally{lock.unlock ();}}} Class Producer implements Runnable{private Resource Res; Producer (Resource res) {this.res=res;} public void Run () {while (true) {Try{res.set ("+ goods +");} catch (Interruptedexception e) {}}}}class Consumer implements runnable{private Resource Res; Consumer (Resource res) {this.res=res;} public void Run () {while (true) {try{res.out ();} catch (Interruptedexception e) {}}}}

Dark Horse Programmer--multi-threaded synchronization of a layer of objects/two-layer objects/three-layer object comparison