如何让 Java 赋值指向一个对象而不是复制? [英] How can Java assignment be made to point to an object instead of making a copy?

问题描述

In a class, I have:

private Foo bar;
public Constructor(Foo bar)
{
    this.bar = bar;
}

Instead of creating a copy of bar from the object provided in the parameter, is it possible to include a pointer to bar in the constructor such that changing the original bar changes the field in this object?

Another way of putting it:

int x = 7;
int y = x;
x = 9;
System.out.print(y); //Prints 7.

It is possible to set it up so that printing y prints 9 instead of 7?

解决方案

Your last example works that way because int is a primitive, it is copied by value. In the first example, "this.bar" would hold a copy of the reference (sort of pointer) to bar. So if you change the original bar (internally), the change will be reflected in your class. Try it.

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