【发布时间】：2011-12-07 04:52:36
【问题描述】：
我一直在尝试验证 ThreadLocal 成员在不同线程中是否确实不同。
这是我在多个线程之间共享其对象的 TestClass。
public class TestClass {
private static Set<Integer> setI;
private static ThreadLocal<Set<String>> setS;
public TestClass() {
Set<String> temp = new HashSet<String>();
for (int i=0; i<=4; i++) {
setI.add(i);
temp.add(Integer.toString(i));
}
setS.set(temp);
}
static {
setI = new HashSet<Integer>();
setS = new ThreadLocal<Set<String>>() {
protected Set<String> initialValue() {
return new HashSet<String>();
}
};
}
public static void addToIntegerSet(int i) {
synchronized(setI) {
setI.add(i);
}
}
public static void addToStringSet(String str) {
Set<String> sets = setS.get();
sets.add(str);
setS.set(sets);
}
}
以下是我用来测试的类：-
package personal;
import java.util.*;
import personal.TestClass;
import java.lang.reflect.Field;
public class Test2 {
private static TestClass testObj;
private static Set<Set<String>> testStringSet;
private static Set<Set<Integer>> testIntegerSet;
static {
testObj = new TestClass();
testStringSet = new HashSet<Set<String>>();
testIntegerSet = new HashSet<Set<Integer>>();
}
private static void addToStringSet(Set<String> sets) {
synchronized(testStringSet) {
testStringSet.add(sets);
}
}
private static void addToIntegerSet(Set<Integer> sets) {
synchronized(testIntegerSet) {
testIntegerSet.add(sets);
}
}
private static int getTestIntegerSetSize() {
synchronized(testIntegerSet) {
return testIntegerSet.size();
}
}
private static int getTestStringSetSize() {
synchronized(testStringSet) {
return testStringSet.size();
}
}
private static class MyRunnable implements Runnable {
private TestClass tc;
private String name;
public MyRunnable(TestClass tc, int i) {
this.name = "Thread:- " + Integer.toString(i);
this.tc = tc;
}
@Override
public void run() {
try {
Field f1 = tc.getClass().getDeclaredField("setS");
Field f2 = tc.getClass().getDeclaredField("setI");
f1.setAccessible(true);
f2.setAccessible(true);
Set<String> v1 = (Set<String>)(((ThreadLocal<Set<String>>)(f1.get(tc))).get());
Set<Integer> v2 = (Set<Integer>) f2.get(tc);
addToIntegerSet(v2);
addToStringSet(v1);
} catch (Exception exp) {
System.out.println(exp);
}
}
}
public static void main(String[] args) {
for (int i=1; i<=2; i++) {
(new Thread (new MyRunnable(testObj,i))).start();
}
try {
Thread.sleep(5);
} catch (Exception exp) {
System.out.println(exp);
}
System.out.println(getTestStringSetSize());
System.out.println(getTestIntegerSetSize());
}
}
因此第一个打印语句应该打印出 2，第二个应该打印出 1。
第一个打印语句也打印出 1。
怎么了？
【问题讨论】：
标签： java multithreading thread-local