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Imagine you have two methods which have exactly the same structure, but differ by methods they call inside. By 'structure' I mean same schemes of logical operators, or callbacks, or internal classes - i.e. everything that defines how the execution flows. Several use-cases possible:

1) both methods are similar but differ by internal calls they make (methodA and methodB)

void callIt(int a, int b) {

if (..) {
  methodA();
}

}

void callIt(int a, int b) {

if (..) {
  methodB();
}

}

2) methods are similar but differ by internal call parameters parameters (i.e. the only difference between the methods is the overloading of some calls inside (methodA) )

void callIt(int a, int b) {

if (..) {
  methodA(a, b);
}

}

void callIt(String a, String) {

if (..) {
  methodA(a, b);
}

}

Is it possible to simplify this code and avoid code repetition?

PS I use Java, but hope it doesn't matter.

Asnwer: Pete Belford gave an answer, if I got him correct - it is described more expanded here: Refactoring methods that use the same code but different types

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KutaBeach
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2 Answers2

1

I think what you are looking for here, is dependency injection.

Assume you have two classes, A & B.

public interface Handler {
  myHandler(int a, int b);
}

public class AHandler implements Handler {....}

public class BHandler implements Handler {....}

Then based upon some criteria, you inject the correct handler into the calling code...

public class MyCaller {
    private Handler handler;  //have a setter.

    public void callIt(int a, int b) {
        handler.myHandler(a, b);
    }
}

Obviously you can use the spring framework to do this injection through configurations, but you could also code your own.

The second part can simply be accomplished my the object oriented concept of overloading. In the interface you could have:

myHandler(int a, int b);
myHandler(String a, String b);

Poor input variable names not withstanding, this is the way many common API methods operate. For example the StringBuilder append method has many different versions that differ only by input parameter.

Pete B.
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  • Pete, do you think this can compile? You pass long values to the method which takes integer parameters. – KutaBeach Aug 23 '13 at 14:23
  • Also, the second case can best be handled by generics, which "allow a type or method to operate on objects of various types while providing compile-time type safety.". http://en.wikipedia.org/wiki/Generics_in_Java – Carl Manaster Aug 23 '13 at 14:26
  • @KutaBeach: corrected to ints. – Pete B. Aug 23 '13 at 14:33
  • Pete, the problem arises when the sets of arguments are different. You have coded the case with the same set of arguments: 2 integers. What should I do if one methods takes 2 ints, and another 2 Strings? – KutaBeach Aug 23 '13 at 14:43
  • Carl, only in case methodA(int a, int b) and methodB(long a, long b) can be rewritten with generics as a single method. – KutaBeach Aug 23 '13 at 14:44
  • Now I got your idea, probably that is what your meant, Pete: http://stackoverflow.com/questions/9688486/refactoring-methods-that-use-the-same-code-but-different-types?rq=1, thanks! – KutaBeach Aug 23 '13 at 15:57
  • @KutaBeach, second case addressed. Also you may want to retag your question with software-engineering. It is more appropriate. – Pete B. Aug 23 '13 at 15:58
0

The first case could be generalized by passing in the method name as a String parameter and call it using reflection.

The second case is much harder since Java isn't good at dynamic casting of values.

Keep in mind that reflection can make your code much harder to read/maintain.

Carl Manaster
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BetaRide
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  • Thanks BetaRide, but using reflection as a refactoring tool is definitely not my case. I just think whether I can invent some trick to avoid copypasting. – KutaBeach Aug 23 '13 at 14:24