Java threads and concurrent libraries advanced applications-thread-scoped shared data threadlocal class

1. Thread-Scoped shared variables

　　

1.1 Prelude:

Use a map to implement thread-scoped shared variables

　　

 Public classThreadscopesharedata {StaticMap<thread, integer> DataMap =NewHashmap<thread, integer>();  Public Static voidMain (string[] args) { for(inti = 0; I < 2; i++) {            NewThread (NewRunnable () {@Override Public voidrun () {intdata =NewRandom (). Nextint ();//get a random integerSystem.out.println (Thread.CurrentThread (). GetName ()+ "Put data" +data);                    Datamap.put (Thread.CurrentThread (), data); NewA (). get (); NewB (). get ();        }}). Start (); }    }    Static classA { Public voidget () {System.out.println (Thread.CurrentThread (). GetName ()+ "Get Data" +Datamap.get (Thread.CurrentThread ())); }    }    Static classB { Public voidget () {System.out.println (Thread.CurrentThread (). GetName ()+ "Get Data" +Datamap.get (Thread.CurrentThread ())); }    }}

　　

The 1.2 threadlocal class is actually a map

/*** ThreadLocal class here ThreadLocal store a variable, if there are multiple variables, you can first encapsulate multiple variables as an object * *@authorAdministrator **/ Public classThreadlocaltest {Staticthreadlocal<integer> x =NewThreadlocal<> ();//     Public Static voidMain (string[] args) {//         for(inti = 0; I < 2; i++) {            NewThread (NewRunnable () {@Override Public voidrun () {intdata =NewRandom (). Nextint ();//get a random integerSystem.out.println (Thread.CurrentThread (). GetName ()+ "Put data" +data);                    X.set (data); NewA (). get (); NewB (). get ();        }}). Start (); }    }    Static classA { Public voidget () {System.out.println (Thread.CurrentThread (). GetName ()+ "Get Data" +x.get ()); }    }    Static classB { Public voidget () {System.out.println (Thread.CurrentThread (). GetName ()+ "Get Data" +x.get ()); }    }}

2. Thread-wide sharing of multiple variables, multiple variables can be encapsulated as an object

/*** ThreadLocal class here ThreadLocal store a variable, if there are multiple variables, you can first encapsulate multiple variables as an object * *@authorAdministrator **/ Public classThreadlocaltest {Staticthreadlocal<integer> x =NewThreadlocal<> ();//     Public Static voidMain (string[] args) {//         for(inti = 0; I < 2; i++) {            NewThread (NewRunnable () {@Override Public voidrun () {intdata =NewRandom (). Nextint ();//get a random integerSystem.out.println (Thread.CurrentThread (). GetName ()+ "Put data" +data);                    X.set (data); Mythreadscopedata MyData= Mythreadscopedata.getthreadinstance ();//gets the object that is bound to the threadMydata.setname ("name" +data);                    Mydata.setage (data); System.out.println (Thread.CurrentThread (). GetName ()+ "put Object" + "Name:" +mydata.getname () + "," + "Age:" +mydata.getage ()); NewA (). get (); NewB (). get ();        }}). Start (); }    }    Static classA { Public voidget () {System.out.println (Thread.CurrentThread (). GetName ()+ "Get Data" +x.get ()); Mythreadscopedata instance= Mythreadscopedata.getthreadinstance ();//directly gets the object associated with the threadSystem.out.println (Thread.CurrentThread (). GetName () + "Get Object" + "Name:" +instance.getname () + "," + "Age:" +instance.getage ()); }    }    Static classB { Public voidget () {System.out.println (Thread.CurrentThread (). GetName ()+ "Get Data" +x.get ()); Mythreadscopedata instance= Mythreadscopedata.getthreadinstance ();//directly gets the object associated with the threadSystem.out.println (Thread.CurrentThread (). GetName () + "Get Object" + "Name:" +instance.getname () + "," + "Age:" +instance.getage ()); }    }}//Single CaseclassMythreadscopedata {//The instance of the class is thread-related, the design of the class is left to the class itself, as long as the call is natural to the thread-relatedPrivate Staticthreadlocal<mythreadscopedata> map =NewThreadlocal<>(); PrivateMythreadscopedata () {} Public StaticMythreadscopedata getthreadinstance () {//threads are independent of each other, and there is no need to consider synchronizationMythreadscopedata instance =Map.get (); if(Instance = =NULL) {instance=NewMythreadscopedata ();        Map.set (instance); }        returninstance; }    PrivateString name; PrivateInteger age; /**     * @returnThe name*/     PublicString GetName () {returnname; }    /**     * @paramName * The name to set*/     Public voidsetName (String name) { This. Name =name; }    /**     * @return The Age*/     PublicInteger getage () {returnAge ; }    /**     * @paramAge * The age to set*/     Public voidsetage (Integer age) { This. Age =Age ; }}

Print results

Thread-1 put data-723086824
Thread-0 put data 772514756
Thread-1 put Object name:name-723086824, age: 723086824
Thread-0 put Object name:name772514756, age:772514756
Thread-0 Get Data 772514756
Thread-1 Get data-723086824
Thread-0 get Object name:name772514756, age:772514756
Thread-1 get Object name:name-723086824, Age: 723086824
Thread-0get Data 772514756
Thread-1get data-723086824
Thread-0 get Object name:name772514756, age:772514756
Thread-1 get Object name:name-723086824, Age: 723086824

Instances of a class are thread-related, the design of the class is left to the class itself, as long as the invocation of nature is a thread-related  strust2 The main idea of this design

See Java API

Threadlocal has a remove () method

You can remove the variables associated with the thread

remove()
Removes the current thread's value for this thread-local variable.

Add:

Virtual machine corresponding class Runtime, there is a methodaddShutdownHook(Thread hook)

　　addShutdownHook(Thread hook)
Registers a new virtual-machine shutdown hook.

For example, you can write a thread that sends a message, and when the virtual machine hangs, it calls the incoming thread, sending a message.

There should also be a mechanism in the thread that can execute a previously registered event before a thread is hung up, or a listener is listening on the state of the thread, thus making callbacks

When you get a notification that the thread hangs, you can remove all the variables related to the thread from the delete

　　

Java threads and concurrent libraries advanced applications-thread-scoped shared data threadlocal class