Multiple inheritance design issue in Java

Question

How do you deal with having only single inheritance in java? Here is my specific problem:

I have three (simplified) classes:

public abstract class A         


        

Answer 1

With your specific example you could use the decorator pattern in conjunction with interfaces to supplement your Word class with additional functionality; e.g.

// *Optional* interface, useful if we wish to reference Words along with
// other classes that support the concept of "length".
public interface Length {
  int getLength();
}

// Decorator class that wraps another Word and provides additional
// functionality.  Could add any additional fields here too.
public class WordExt extends AbstractWord implements Length {
  private final Word word;

  public class(Word word) {
    this.word = word;
  }

  public int getLength() {
    return word.getKind().length();
  }
}

In addition it's worth noting that the lack of multiple inheritence in Java isn't really the issue here; it's more a case of reworking your design. In general it's considered bad practice to over-use inheritence as deep inheritence hierarchies are difficult to interpret / maintain.