for Java, is Class.newInstance() thread safe

Question

a part of code like this:

class Test {

private static final Map<String, Class> urlHandlers = new ConcurrentHashMap<String, Class>();
static {
    urlHandlers.put(urlRegexA, HandlerA.class);
    urlHandlers.put(urlRegexB, HandlerB.class);
    ...
}
public Handler handle(String url) {
    ......
    if(url match urlRegex) {
        Class claz = urlHandlers.get(urlRegex);
        //in multi-thread environment, is it thread-safe?
        return claz.newInstance();
    }
}
}

I want to known whether Class.newInstance() is thread safe? anyone know this?

Answer 1

The javadoc states

The class is instantiated as if by a new expression with an empty argument list.

So it is equivalent to doing

new YourClass();

So it depends entirely on if your YourClass constructor is thread safe.

Answer 2

是的，只要构造函数对对象的静态内容不执行任何非线程安全的操作，这是线程安全的。