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!