Detect a change in the value of an object passed as a parameter

Question

Now I am working with code similar to this

public String getName(User user) {
     user.setSth(...);
     return user.getName();
}

It seems to me that the wrong practice is to modify objects passed as parameters. Is there a tool that detects such code? I looked at findbugs, pmd and checkstyle, but could not find any check for this.

PS sorry for the bad example.

Answer 1

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Answer 2

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Answer 3

User ( final, final . , , , ).

- "", , newId :

public final class User {
    private final String name;
    private final int id;

    User(String name, int id) {
        this.name = name;
        this.id = id;
    }

    public User newId(int newId) {
        return new User(this.name, newId);
    }

    //getters here;
}

String, Integer,... .

Answer 4

UserView, "getters", UserView .

interface UserView{
 public String getName();
...

class User implements UserView...

public String getName(UserView user) {
     user.setSth(...); // Will not compile
     return user.getName();
}

Answer 5

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Answer 6

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:

http://prog.vub.ac.be/DMP/

http://www.cs.bris.ac.uk/Publications/pub_master.jsp?id=1000273

http://www.google.com/search?num=100&hl=en&q=Declarative+Metaprogramming

Answer 7

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You claim that it is “bad,” because side effects like this can surprise the user. It is true, but it is only harmful if it is an undesirable surprise.