Building big, immutable objects without using constructors having long parameter lists

Question

I have some big (more than 3 fields) objects that can and should be immutable. Every time I run into that case I tend to create constructor abominations with long parameter

Answer 1

Here are a couple of more options:

Option 1

Make the implementation itself mutable, but separate the interfaces that it exposes to mutable and immutable. This is taken from the Swing library design.

public interface Foo {
  X getX();
  Y getY();
}

public interface MutableFoo extends Foo {
  void setX(X x);
  void setY(Y y);
}

public class FooImpl implements MutableFoo {...}

public SomeClassThatUsesFoo {
  public Foo makeFoo(...) {
    MutableFoo ret = new MutableFoo...
    ret.setX(...);
    ret.setY(...);
    return ret; // As Foo, not MutableFoo
  }
}

Option 2

If your application contains a large but pre-defined set of immutable objects (e.g., configuration objects), you might consider using the Spring framework.