public class Student {  
  private int age=0;       
  public int getAge() {  
      return this.age;  

  }  

   public void setAge(int age) {  
       this.age = age;  
   }  
 }

    public class TreadLocalDemo implements Runnable {  
       private final static  ThreadLocal studentLocal = new ThreadLocal();  

       public static void main(String[] agrs) {  
           TreadLocalDemo td = new TreadLocalDemo();  
             Thread t1 = new Thread(td,"a");  
             Thread t2 = new Thread(td,"b");  

            t1.start();  
           t2.start();  

         }  


       public void run() {  
            accessStudent();  
        }  

       public  void  accessStudent() {  

           String currentThreadName = Thread.currentThread().getName();  
           System.out.println(currentThreadName+" is running!");  
           Random random = new Random();  
           int age = random.nextInt(100);  
           System.out.println("thread "+currentThreadName +" set age to:"+age);  
           Student student = getStudent();  
           student.setAge(age);  
           System.out.println("thread "+currentThreadName+" first  read age is:"+student.getAge());  
           try {  
           Thread.sleep(5000);  
           }  
           catch(InterruptedException ex) {  
               ex.printStackTrace();  
           }  
           System.out.println("thread "+currentThreadName +" second read age is:"+student.getAge());  

       }  

       protected Student getStudent() {  
           Student student = (Student)studentLocal.get();  
          if(student == null) {  
               student = new Student();  
               studentLocal.set(student);  
           }  
           return student;  
       }  

       protected void setStudent(Student student) {  
           studentLocal.set(student);  
       }  
  }  
 

    public class ThreadLocal  
    {  
    　private Map values = Collections.synchronizedMap(new HashMap());  
    　public Object get()  
    　{  
    　　Thread curThread = Thread.currentThread();   
    　　Object o = values.get(curThread);   
   　　if (o == null && !values.containsKey(curThread))  
   　　{  
  　　　o = initialValue();  
  　　　values.put(curThread, o);   
  　　}  
   　　return o;   
   　}  

   　public void set(Object newValue)  
   　{  
  　　values.put(Thread.currentThread(), newValue);  
   　}  

   　public Object initialValue()  
   　{  
   　　return null;   
   　}  
   }