Java assigning a new value to a parameter, is this considered a bad practice?

Question

I have read the question here: http://stackoverflow.com/questions/2229389/is-it-problematic-to-assign-a-new-value-to-a-method-parameter. However it is not clear to me if doing something like:

public void myMethod(Object obj) {
    doSomething(obj);
    obj = getNewObj();
}

or:

public void anotherMethod(Object obj) {
     obj = doSomething(obj):
}

This is basically just to avoid declaring a new local variable, is this worth it?, is this seen as a bad practice?.

Answer 1

Performance 0, Readability -1. I wish eclipse could add final tags automatically.

Answer 2

This is a bad practice. You will be hard pressed to find a scenario where the sacrificed readability is worth it. This will be especially confusing to anyone who doesn't understand Java's "pass by value" policy, which sadly is a lot of people.