isThreadCpuTimeSupported返回负数

Question

我一直在为此扯头发。我的程序应该在使用简单的双哈希算法搜索哈希表时测量CPU时间。但是，ThreadMXBean不断返回-1。任何帮助表示赞赏。

“主要”代码段

ThreadMXBean bean = ManagementFactory.getThreadMXBean();
    //CREATE A THREAD
    DoubleHashThread doubleThread = 
            new DoubleHashThread("doublethread"); //CREATE DOUBLE HASHING THREAD
    doubleThread.setDaemon(true);
    doubleThread.start();

    getCpuTime(doubleThread);
    doubleThread.run(hashTable,data); //RUN SEARCH FUNCTION
    getCpuTime(doubleThread);

GetCpuTime方法

public static long getCpuTime(DoubleHashThread dt)
{
    ThreadMXBean bean = ManagementFactory.getThreadMXBean(); //GET THREAD BEAN
    long cpuTime = 0;

    if (bean.isThreadCpuTimeSupported()) //if grabbing it is supported, continue
    {
        System.out.println("CPU time for " + dt.getId() + " " + dt.getName() + 
                           " is " + bean.getThreadCpuTime(dt.getId()));
    }

    return cpuTime;

}

DoubleHashThread.java

import doubleHash.DoubleHash;
public class DoubleHashThread extends Thread
{
    public DoubleHashThread(String s) 
    {
        this.setName(s);
    }

    //RUNS SEARCH FUNCTION
    public void run(String[] hashTable, String data)
    {
        DoubleHash.searchTable(hashTable,data); //run Double Hash's search
    }
}