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IntelliJ 8: Introduce Parameter Refactoring

06 Nov, 2008

IntelliJ 8 provides 7 new refactorings. One new powerful refactoring is the Introduce Parameter Object. The name speaks for itself: it introduces a parameter object! But what does it really do? The refactoring promotes good encapsulation. It encapsulates fields by introducing a new object for them.

For example, you might encounter or write the following piece of code:

public class Parser {
    public void parse(String firstName, String lastName) {
       // firstName and lastName handling here
    }
    public void testParser() {
        new Parser().parse("erik", "pragt");
    }
}

The method call consists of two Strings, but a better approach might be to encapsulate those fields into a new class, for example ‘Name’. This refactoring does exactly that. Just select the ‘parse’ method, go to Refactor -> Introduce Parameter Object, which will look like:

public class Name {
    private final String firstName;
    private final String lastName;
    public Name(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
    public String getFirstName() {
        return firstName;
    }
    public String getLastName() {
        return lastName;
    }
}
public class Parser {
    public void parse(Name name) {
      // name handling here
    }
    public void testParser() {
        new Parser().parse(new Name("erik", "pragt"));
    }
}

After refactoring, you’re code will look like this, which is a much better typed version of the previous one!

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Vikas Hazrati
13 years ago

Eclipse has it 🙂
Select the parameters, Alt+Shft+T –> Introduce Parameter Object

raveman
raveman
13 years ago

I bet IntelliJ had that feature first 😛 lol

Erik Pragt
13 years ago

Well, ehhmm,…this is a *new* refactoring… But I guess it’s good that IntelliJ finally borrows something back! 😉

florin
florin
13 years ago

And then you have to introduce another “Parameter Object” to the Name class that will take two parameters:
@Constructor
public Person(PersonParameters parameters) {
this.firstName = parameters.getFirstName();
this.lastName = parameters.getLastName();
}
with resulting code:
parser = new Parser(new Name(parameters));
etc…
is @Re-curse a reserved annotation or a keyword to be filtered?
I love it.

Aziz Kadhi
Aziz Kadhi
13 years ago

Which version are you using? I am using 8.0M1 and I don’t seem to be able to find it.
Thanks

Aziz Kadhi
Aziz Kadhi
13 years ago

Never mind. I have just learned that the final 8.0 release is out.

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