Java Atomic Reference Atomicreference

Link: https://www.jianshu.com/p/882d0e2c3ea6: Jane book full-time Atomicreference

An object reference the May updated atomically.

AtomicReferenceThe class provides reference objects. May is read and written atomically, so if multiple threads try to reach them at the same time, only one would be able to doing so.
Provides a read-write atomic operation of a reference variable.

The following methods are provided:

• compareAndSet(V expect, V update): atomically Sets the value to the given updated value if the current value == the expected value .
• getAndSet(V newValue): atomically sets to the given value and returns the old value.
• lazySet(V newValue): Eventually sets to the given value.
• set(V newValue): Sets to the given value.
• get(): Gets the current value.

Suppose there is a class person, which is defined as follows:

Classperson {private String name;Privateint age;PublicPerson(String name,int age) {THIS.name = name;This.age = age; }Public StringGetName() {return name; }PublicvoidSetName(String name) {this.name = name;} public int getage () {return age;} public void setAge  (int age) {this.age = age;} public String tostring () {return " [Name: "+ this.name +  "Age:" + this.age + Span class= "hljs-string" > "]"; }} 

If you use normal object references, updating objects in multithreaded situations can cause inconsistencies. For example:
The initial state of an object is name=Tom, age = 18 .
Thread 1 will name be modified to Tom1 , age + 1 .
Thread 2 will name be modified to Tom2 , age + 2 .

We think that there will only be two kinds of results:

• If thread 1 executes first, thread 2 executes, the middle state is name=Tom1, age = 19 , and the result state is name=Tom2, age = 21
• If thread 2 executes first, thread 1 executes, the middle state is name=Tom2, age = 20 , and the result state is name=Tom1, age = 21

However, the possible output is as follows:

Person is [Name:tom, age:18]
Thread2 Values [Name:tom1, age:21]
Thread1 Values [Name:tom1, age:21]
Now person is [name:tom1, age:21]

General referencesPrivatestatic person person;PublicStaticvoidMain(string[] args)Throws Interruptedexception {person =New Person ("Tom,"18); System.out.println ("Person is" + person.tostring ()); Thread T1 =New Thread (New Task1 ()); Thread t2 =New Thread (New Task2 ()); T1.start (); T2.start (); T1.join (); T2.join (); System.out.println ("Now person is" + person.tostring ());}StaticClassTask1ImplementsRunnable {Publicvoid run () {Person.setAge ( Person.getage () + 1); Person.setname ( "Tom1"); System.out.println ( "Thread1 Values" + person.tostring ());}} static class task2 implements Runnable {public void run () {Person.setage (Person.getage () + 2); Person.setname ( "Tom2"); System.out.println ( "Thread2 Values" + person.tostring ())}}     

If you use an Atomic object reference, updating an object in a multithreaded situation ensures consistency. For example:

General referencesPrivatestatic person person;Atomic ReferencesPrivateStatic atomicreference<person> Arperson;PublicStaticvoidMain(string[] args)Throws Interruptedexception {person =New Person ("Tom,"18); Arperson =New atomicreference<person> (person); System.out.println ("Atomic person is" + arperson.get (). toString ()); Thread T1 =New Thread (New Task1 ()); Thread t2 =New Thread (New Task2 ()); T1.start (); T2.start (); T1.join (); T2.join (); System.out.println ("Now Atomic person is" + arperson.get (). toString ());}StaticClassTask1ImplementsRunnable {PublicvoidRun() {Arperson.getandset (new person ( "Tom1", Arperson.get (). Getage () + 1)"); System.out.println ( "Thread1 Atomic References" + arperson.get (). toString ());}} static class task2 implements Runnable {public void run () {Arperson.getandset (new Person ( "Tom2", Arperson.get (). Getage () + 2)); System.out.println ( "Thread2 Atomic References" + arperson.get (). toString ());}}    

However, the possible output is as follows:

Atomic person is [Name:tom, age:18]
Thread1 Atomic References [Name:tom1, age:19]
Thread2 Atomic References [Name:tom2, age:21]
Now Atomic person is [Name:tom2, age:21]

Reference:
Java atomicreference Example

(RPM) Java Atomic Reference atomicreference