工厂模式例子之计算器的实现
1 这里是一个计算器,运算规则为 加减乘除,输出相应的结果
2 UML图
3 java类
Counter.java (抽象接口)
package DesignPattern.calculator;
public interface Counter {
public double getResult();
}
package DesignPattern.calculator;
public class AddCounter implements Counter {
private double x;
private double y;
public AddCounter(double x,double y){
this.x = x;
this.y = y;
}
@Override
public double getResult() {
return this.x + this.y;
}
}
DivCounter.java (减法类)
package DesignPattern.calculator;
public class DivCounter implements Counter {
private double x;
private double y;
public DivCounter(double x,double y){
this.x = x;
this.y = y;
}
@Override
public double getResult() {
return this.x - this.y;
}
}
MulCounter.java (乘法类)
package DesignPattern.calculator;
public class MulCounter implements Counter {
private double x;
private double y;
public MulCounter(double x,double y){
this.x = x;
this.y = y;
}
@Override
public double getResult() {
return this.x * this.y;
}
}
SubCounter.java (除法类)
package DesignPattern.calculator;
public class SubCounter implements Counter {
private double x;
private double y;
public SubCounter(double x,double y){
this.x = x;
this.y = y;
}
@Override
public double getResult() {
double result = 0;
if(this.y == 0){
try {
throw new MyException("被除数为0");
} catch (MyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else{
result = this.x/this.y;
}
return result;
}
}
ErrorCounter.java (未知规则,如果客户端传错了类型,则调用该类)
package DesignPattern.calculator;
public class ErrorCounter implements Counter {
private double x;
private double y;
public ErrorCounter(double x,double y){
this.x = x;
this.y = y;
}
@Override
public double getResult() {
try {
throw new MyException("异常:错误的计算类");
} catch (MyException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return 0;
}
}
package DesignPattern.calculator;
public class MyException extends Exception {
public MyException(String str){
System.out.println(str);
}
}
Client.java (客户端)
package DesignPattern.calculator;
public class Client {
public static void main(String[] args) {
double x = 10,y =20;
Counter Counter;
// 加法
Counter = Factory.createCounter('+', x, y);
System.out.println("加法结果为 : " + Counter.getResult());
//减法
Counter = Factory.createCounter('-', x, y);
System.out.println("减法的结果为 : " + Counter.getResult());
//乘法
Counter = Factory.createCounter('*', x, y);
System.out.println("乘法的结果为 : " + Counter.getResult());
//除法
Counter = Factory.createCounter('/', x, y);
System.out.println("除法的结果为 : " + Counter.getResult());
//除法 ,被除数为0
Counter = Factory.createCounter('/', x, 0);
System.out.println("除法的结果为 : " + Counter.getResult());
//未知
Counter = Factory.createCounter('?', x, y);
System.out.println("未知规则的结果 : " + Counter.getResult());
}
}
4 输出结果
