本文通过简单通俗的例子, 告诉我们如何判断代码的稳定性和代码中的异类, 并且如何重构此类代码.
异味这个词,可能有点抽象,我们先看一下下面的例子
这是一个CAD系统. 现在,它已经可以画三种形状了:线条,长方形,跟圆.先认真的看一下下面的代码:
class Shape {
final static int TYPELINE = 0;
final static int TYPERECTANGLE = 1;
final static int TYPECIRCLE = 2;
int shapeType;
//线条的开始点
//长方形左下角的点
//圆心
Point p1;
//线条的结束点
//长方形的右上角的点
//如果是圆的话,这个属性不用
Point p2;
int radius;
}
class CADApp {
void drawShapes(Graphics graphics, Shape shapes[]) {
for (int i = 0; i < shapes.length; i ) {
switch (shapes[i].getType()) {
case Shape.TYPELINE:
graphics.drawLine(shapes[i].getP1(), shapes[i].getP2());
break;
case Shape.TYPERECTANGLE:
//画四条边
graphics.drawLine(...);
graphics.drawLine(...);
graphics.drawLine(...);
graphics.drawLine(...);
break;
case Shape.TYPECIRCLE:
graphics.drawCircle(shapes[i].getP1(), shapes[i].getRadius());
break;
}
}
}
}
代码都是一直在改变的,而这也是上面的代码会碰到的一个问题.
现在我们有一个问题: 如果我们需要支持更多的形状(比如三角形), 那么肯定要改动Shape这个类, CADApp里面的drawShapes这个方法也要改.
好,改为如下的样子:
class Shape {
final static int TYPELINE = 0;
final static int TYPERECTANGLE = 1;
final static int TYPECIRCLE = 2;
final static int TYPETRIANGLE = 3;
int shapeType;
Point p1;
Point p2;
//三角形的第三个点.
Point p3;
int radius;
}
class CADApp {
void drawShapes(Graphics graphics, Shape shapes[]) {
for (int i = 0; i < shapes.length; i ) {
switch (shapes[i].getType()) {
case Shape.TYPELINE:
graphics.drawLine(shapes[i].getP1(), shapes[i].getP2());
break;
case Shape.TYPERECTANGLE:
//画四条边.
graphics.drawLine(...);
graphics.drawLine(...);
graphics.drawLine(...);
graphics.drawLine(...);
break;
case Shape.TYPECIRCLE:
graphics.drawCircle(shapes[i].getP1(), shapes[i].getRadius());
break;
case Shape.TYPETRIANGLE:
graphics.drawLine(shapes[i].getP1(), shapes[i].getP2());
graphics.drawLine(shapes[i].getP2(), shapes[i].getP3());
graphics.drawLine(shapes[i].getP3(), shapes[i].getP1());
