Self Encapsulate Field(自封装字段)

private int _low, _heigh;
boolean includes(int arg){
  return arg >= _low && arg <= _high;
}

修改为：

private int _low, _heigh;
boolean includes(int arg){
  return arg >= getLow() && arg <= getHeigh();
}
int getLow(){return _low}
int getHeigh(){return _heigh}

做法

• 为待封装字段建立取值/设值函数

• 找出该字段的所有引用点，将它们全部改为调用取值/设值函数

  如果引用点要读取字段值，就将它替换为调用取值函数；如果引用点要给字段赋值，就将它替换为调用设值函数

你可以暂时将该字段改名，让编译器帮助你查找引用点

• 将该字段声明为private

• 复查，确保找出所有引用点

• 编译，测试

范例

class IntRange{
  private int _low, _high;
  boolean includes(int arg){
    return arg >= _low && arg <= _high;
  }
  void grow(int factor){
    _high = _high * factor;
  }
  IntRange(int low, int high){
    _low = low;
    _high = high;
  } 
}

修改后：

class IntRange{
  boolean includes(int arg){
    return arg >= _low && arg <= _high;
  }
  void grow(int factor){
    _high = _high * factor;
  }
  private int _low, _high;
  int getLow(){
    return _low;
  }
  int getHigh(){
    return _high;
  }
  void setLow(int arg){
    _low = arg;
  }
  void setHigh(int arg){
    _high = arg;
  }
  IntRange(int low, int high){
    initialize(low,high)
  } 
  private void initialize(int low, int high){
      _low = low;
    _high = high;
  }
}