enum DocumentState
{
    readonly,Editable
}

class Document
{
 DocumentState state;
 public void Handle()
 {
  if(state=DocumentState.readonly)
  {
  }
  else
  {
  }
 }
}
-------------------------------------
abstract clasass StatedDocument  ---表达状态及依赖的行为
{
 public abstract void Handle1()
 public abstract void Handle2()
 public abstract void Handle3()
 public abstract StatedDocument Next
        { get;set;}
}

class Document------Request
{
 StatedDocument statedDocument;
 public void SetStatedDocument(StatedDocument statedDocument)
 {
  this.statedDocument=statedDocument;
 }
 public void Handle1()
 {
  statedDocument.Handle1();
 }
 public void Handle2()
 {
  statedDocument.Handle2();
 }
 public void Handle3()
 {
  statedDocument.Handle3();
 }
}

-----------具体的状态类

public class ReadOnlyDocumentState:StatedDocument 

{

　　 public abstract void Handle1()--------edit button

      {

　　　　　　system.println(" system is readonly");

　　　　　　SetStatedDocument(new EditableDocumentState)

      }

}