Java Singleton Design Pattern implementation

Can the implementation for a Singleton class can be as simple as below :

public class MyClass {
    private final static MyClass myClass = new MyClass();
    public static MyClass getInstance() {
        return myClass;
    }
}

Over :

public class MyClass {
    private final static MyClass myClass;
    public static MyClass getInstance() {
        if(null == myClass) {
            myClass = new MyClass();
        }
        return myClass;
    }
}

Which is the better of the above implementations & why?

One thing that I observed is for the first implementation above the object constructor gets called before the static block if any.

Also if there is a thread-safe version of the 2nd implementation (may be a double null check and synchronized block), which should be preferred ?