在JAVA中通过ref，double和Double传递参数

Question

If someone could help me understand the following problem:

As I understand double is primitive data type in Java and Double is immutable class. Every parameter is passed by value. If it is primitive type ( int , double , byte ), then it is the actual value that is passed; and if it is an object type, then it is the address to that object that is copied.

If that is so, why this parameter that is of type Double is not changed?

...
    public static void main(String[] args) {
        Double value = new Double(0);

        SomeObj so = new SomeObj();
        so.setNewValue(value);

        System.out.println(value);
    }
...

public class SomeObj {
    public void setNewValue(Double changeMe)
    {
        changeMe = new Double(10.0);
    }
}

Answer 1

It is the reference to the object that is passed by value . In the setNewValue method, you change the reference, so the changeMe variable points to something else. The (reference to the) original value object in the main method is not changed.

see also Is Java "pass-by-reference" or "pass-by-value"?