Using threadlocal to generate unique identities and implementation principles for threads

1, in multithreaded programming, sometimes need to automatically generates each start line into a unique identity, this time, through a threadlocal variable to save the identity of each thread is the most effective, most convenient way.

2. ThreadLocal instances are typically private static fields in a class

3, in the construction of threadlocal, by overriding the subclass of the method to rewrite the sequence number. The purpose of generating the serial number for each thread is thus achieved.

Importjava.util.Collections;ImportJava.util.HashMap;ImportJava.util.Map;/*** A multithreaded object with a private variable serialnum that holds the ordinal number of the object thread *@authorYinchuan.chen **/classMultithreadobjectextendsThread {//Line program number variable    PrivateSerialnum Serialnum;  PublicMultithreadobject (Serialnum serialnum) {//Initialize line program number save variable         This. Serialnum =Serialnum; }     /*** A schematic multi-threaded business approach*/      Public voidrun () {System.out.println ("Thread" + thread.currentthread (). GetName () + "The serial number is" +serialnum.getnextnum ()); } }/*** A schematic threadlocal implementation that is equivalent to the Threadlocal API in the JDK *@authorYinchuan.chen **/classsimplethreadlocal {//a thread map to hold the thread and its corresponding variable copy    PrivateMap Threadmap = Collections.synchronizedmap (NewHashMap ());  Public voidset (Object object) {Threadmap.put (Thread.CurrentThread (), object); }      PublicObject Get () {Thread CurrentThread=Thread.CurrentThread (); Object obj=Threadmap.get (CurrentThread); if(obj = =NULL&&!Threadmap.containskey (CurrentThread)) {obj=InitialValue ();         Threadmap.put (CurrentThread, obj); }         returnobj; }      Public voidRemove () {Threadmap.remove (Thread.CurrentThread ()); }     protectedObject InitialValue () {return NULL; } }/*** Line Program number identification generation tool *@authorYinchuan.chen **/classSerialnum {//class-level thread number variable, pointing to the ordinal of the next thread    Private StaticInteger nextnum = 0; //defines a threadlocal variable that holds an integer type of line program number//private static threadlocal<integer> Threadno = new threadlocal<integer> () {    Private StaticSimplethreadlocal Threadno =Newsimplethreadlocal () {//subclasses of threadlocal are defined by anonymous inner classes, overriding the InitialValue () method         Public synchronizedInteger InitialValue () {returnnextnum++;     }     }; /*** Get Line program number * *@returnLine Program number*/      Public intGetnextnum () {return(Integer) threadno.get (); } } Public classtesttreadlocal { Public Static voidMain (string[] args) {serialnum serialnum=NewSerialnum (); Multithreadobject M1=NewMultithreadobject (Serialnum); Multithreadobject m2=NewMultithreadobject (Serialnum); Multithreadobject M3=NewMultithreadobject (Serialnum); Multithreadobject M4=NewMultithreadobject (Serialnum);         M1.start ();         M2.start ();         M3.start ();         M4.start (); //The following test method is in the main thread, where the current threads areTestmainthread (); }      Public Static voidTestmainthread () {serialnum serialnum=NewSerialnum (); System.out.println ("Serial number of the main thread is" +serialnum.getnextnum ()); Serialnum serialNum2=NewSerialnum (); System.out.println ("Serial number of the main thread is" +serialnum2.getnextnum ()); } }

Using threadlocal to generate unique identities and implementation principles for threads