gistfile1.java

abstract class Base {
  protected String aaa;
  public Base setAaa(String aaa) {
    this.aaa = aaa;
    return this;
  }
}

class Hoge extends Base {
  protected String xxx;
  public Hoge setXxx(String xxx) {
    this.xxx = xxx;
    return this;
  }
}

new Hoge().setAaa("").setXxx("")
                   ↑BaseのやつはChainできない..

どうやるのがスマートかなぁ・・

こうか？
abstract class Base <T extends Base<T>> {
  protected String aaa;
  public T setAaa(String aaa) {
    this.aaa = aaa;
    return (T) this;
  }
}

class Hoge extends Base<Hoge> {
  protected String xxx;
  public Hoge setXxx(String xxx) {
    this.xxx = xxx;
    return this;
  }
}