Thread.activeCount()运行出错问题

......

    System.out.println(Thread.activeCount());

    while (Thread.activeCount() > 1) {

      Thread.yield();

    }

    System.out.println(t.getNum());

按照教程中写的代码

打印结果：

877

1000

FATAL ERROR in native method: JDWP cannot get thread local storage, jvmtiError=JVMTI_ERROR_WRONG_PHASE(112)

JDWP exit error JVMTI_ERROR_WRONG_PHASE(112): cannot get thread local storage [../../../src/share/back/threadControl.c:195]

为什么有警告输出？