直接访问一个字段，但与字段之间的耦合关系逐渐变得笨拙

private int low;
private int high;boolean includes(int arg) {return arg >= low && arg <= high;
}

重构：为这个字段建立get/set函数，并以这些函数访问字段

private int low;
private int high;public int getLow() {return low;
}public int getHigh() {return high;
}public boolean includes(int arg) {return arg >= getLow() && arg <= getHeigh();
}