MutexLocker ml(Heap_lock)；

常见写法

jvm源码有很多这种类型写法的代码
MutexLocker ml(Heap_lock);
ObjectWaiter node(Self);
…

上面这种语法，对java程序员应该没接触过

这里以MutexLocker举例

MutexLocker ml(Heap_lock);

MutexLocker

class MutexLocker: StackObj {
 private:
  Monitor * _mutex;
 public:
  MutexLocker(Monitor * mutex) { // MutexLocker ml(Heap_lock); 调用该构造函数
    assert(mutex->rank() != Mutex::special,
      "Special ranked mutex should only use MutexLockerEx");
    _mutex = mutex;
    _mutex->lock();
  }
 .............
}

java写法

# c++ 
MutexLocker ml(Heap_lock);

# java
MutexLocker ml = new MutexLocker(Heap_lock);