Java favorite refactoring techniques [closed]

Question

There are some common code patterns I find in other people's Java code that can benefit from some simple refactoring.

What are your pet code pattern hates and their fixes (and the reason if it isn't obvious)?

I have taken to liberty of answering with a couple of my own pet hates.

Answer 1

One of my favourite refactoring is using Strategy pattern instead of long if-else/switch statments. Eg.

String chooser = ""//some sting

if(testCond1(chooser)){
doSomething1();
} else if(testCond2(chooser)){
doSomethingElse2();
} else if(testCond2(chooser)){
doSomethingElse3();
} else if(testCond4(chooser)){
doSomethingElse4();
} else if(testCond5(chooser)){
doSomethingElse5();
} else if(testCond6(chooser)){
doSomethingElse6();
}

Can be changed to:

    Map<String, Handler> handlers = new HashMap<String, Handler>();

handlers.get(chooser).handle();

then we define a Handler interface

interface Handler{
    handle();
}

And for each condition we have a new class that implements the handler.

class CondOne implements Handler{
    handle(){
        //some code
    }
}

Pros. Object oriented approch, code is easier to maintain. It is also easy to add new conditions without changing the important parts of the code.

Answer 2

I like enums and try to refactor code with a lot of string checks.

if (str.equals("A") {...}
else if (str.equals("B") {...}
else if (str.equals("C") {...}

to

switch (str){
 case A: ... ; break;
 case B: ... ; break;
 case C: ... ; break;

}