Null Object Pattern Example

Account.java

public interface Account extends Nullable {
  
  final static NULL = new NullAccount();
  
  String getName();
  String getDescription();
  
  // Whether or not this account can be used to conduct business
  boolean isActive();
  
  // Whether or not the internal state of this account is valid
  boolean isValid();
  
  private final class NullAccount implements Account {
    
    private NullAccount() {
      super();
    } 
    
    @Override
    public boolean isNull() {
      return true;
    }

    @Override
    public String getName() {
      return "";
    }
    
    @Override
    public Sting getDescription() {
      return "";
    }
    
    @Override
    public boolean isActive() {
      return false;
    }
    
    @Override
    public boolean isValid() {
      return true;
    }
    
    @Override
    public String toString() {
      return "Null Account";
    }
    
  }
  
}

Nullable.java

public interface Nullable {

  boolean isNull();

}