Part 2 thread Security (2) -- threadlocal variable

As mentioned above, the variable security issue.

1. Try not to let the thread run on the same object instance. This is a relatively low-efficiency method. In some cases, sharing objects between threads is inevitable.

2. encapsulate variables that may be shared in a method to make it an internal variable of the method. In this way, every thread has its own private variable value even if multiple threads concurrently execute this method.

The second method is relatively recommended.

The threadlocal variable is introduced below: A threadlocal variable can only store one proprietary object, if the thread needs multiple proprietary objects. Multiple threadlocal variables need to be designed.

The following code is used to understand threadlocal [threadlocaltest]

/** <Br/> * threadlocaltest. java <br/> * copyright (c) 2011 cuiran2001@163.com <br/> * Create: cui ran 2011-1-13 04:11:56 <br/> */</P> <p> package COM. cayden. thread812; </P> <p>/** <br/> * @ author Cui ran <br/> * @ version 1.0.0 <br/> * @ DESC <br/> */ <br/> public class threadlocaltest {</P> <p>/** <br/> * @ Param ARGs <br/> */<br/> Public static void main (string [] ARGs) {<br/> // todo auto-generated method stub <br/> runnable accumelatora = new accumulatort (); </P> <p> thread threada = new thread (accumelatora, "threada"); <br/> thread threadb = new thread (accumelatora, "threadb"); </P> <p> threada. start (); <br/> threadb. start (); <br/>}</P> <p >}< br/> class accumulatort implements runnable <br/>{</P> <p> threadlocal = new threadlocal (); <br/> @ override <br/> Public void run () {<br/> // todo auto-generated method stub </P> <p> for (INT I = 1; I <= 10; I ++) {<br/> If (threadlocal. get () = NULL) </P> <p> threadlocal. set (New INTEGER (0); </P> <p> int x = (integer) threadlocal. get ()). intvalue (); </P> <p> X = x + I; <br/> threadlocal. set (New INTEGER (x); <br/> try {<br/> thread. sleep (1000); <br/>} catch (interruptedexception e) {<br/> // todo: handle exception <br/>}< br/> system. out. println (thread. currentthread (). getname () + "/T accumulate and =" + (integer) threadlocal. get ()). intvalue (); <br/>}</P> <p>}

Running result:

Threada accumulate and = 1 <br/> threadb accumulate and = 1 <br/> threadb accumulate and = 3 <br/> threada accumulate and = 3 <br/> threada accumulate and = 6 <br/> threadb accumulation and = 6 <br/> threadb accumulation and = 10 <br/> threada accumulation and = 10 <br/> threada accumulation and = 15 <br/> threadb accumulation and = 15 <br/> threadb accumulation and = 21 <br/> threada accumulation and = 21 <br/> threada accumulation and = 28 <br/> threadb accumulation and = 28 <br/> threadb accumulation and = 36 <br/> threada accumulation and = 36 <br/> threada accumulation and = 45 <br/> threadb accumulation and = 45 <br /> threada accumulate and = 55 <br/> threadb accumulate and = 55 <br/>

Threadlocal is an advanced technique of multi-threaded programming and the ultimate solution to variable security issues. Storing variables that may have shared conflicts in threadlocal variables can effectively prevent tampering by other threads running the same code. Threadlocal establishes a one-to-one binding relationship between variables and threads.