----关于类对象作为函数返回值的问题------

Question

public CLASSNAME getBNFRule(String ruleName)
  {
    for(int leafNum=0; leafNum<List.size(); leafNum++)
    {
      String leafName = ((CLASSNAME)List.get(leafNum)).getName();
      if(leafName.compareTo(ruleName) ==0)
      {
        return (CLASSNAME)List.get(leafNum);
      } 
      else
      {
       return null;
      }    
    }
    //here
    return null;
  }

Answer 1

你这样写程序，当for循环执行第一次时，如果leafName.compareTo(ruleName) ==0为false，就执行else里语句，返回null了。
应该这样写。
public CLASSNAME getBNFRule(String ruleName)
  {
    int count = List.size();      //记录总数
    for(int leafNum=0; leafNum<count; leafNum++)
    {
      String leafName = ((CLASSNAME)List.get(leafNum)).getName();
      if(leafName!=null && leafName.equals(ruleName))
      {
        return (CLASSNAME)List.get(leafNum);
      }  
    }    return null;  }