Question

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Long list of if statements in Java

I was tasked to work with some code, and there is a giant if-else-if chain (100+ else-ifs) that checks Strings.

What are some good techniques to update this code as to where the if-else-if chain can be shrunken down to something much more manageable.

The chain looks something like this:

if(name.equals("abc")){
    do something
} else if(name.equals("xyz")){
    do something different
} else if(name.equals("mno")){
    do something different
} ......
.....
else{ 
   error
}

Answer 1

You can extract the code in each branch to a separate method, then turn the methods into implementations of a common base interface (let’s call it Handler). After that, you can fill a Map<String, Handler> and just look up and execute the right handler for given string.

Unfortunately the implementation of 100+ subclasses for the interface requires quite a lot of boilerplate code, but currently there is no simpler way in Java to achieve this. Implementing the cases as elements of an Enum may help somewhat – here is an example. The ideal solution would be using closures / lambdas, but alas we have to wait till Java 8 for that…