一、简单工厂模式:
实质是由一个工厂类根据传入的参数，动态决定应该创建哪一个产品类（这些产品类继承自一个父类或接口）的实例。简单工厂模式的创建目标，所有创建的对象都是充当这个角色的某个具体类的实例。
二、场景
使用Java面向对象语言实现一个计算机控制台程序，要求输入两个数和运算符号，得到结果。
为了使程序达到易扩展，易维护，易复用且灵活的目的，本程序将使用到面向对象编程思想的三大特性：封装、继承和多态，以及简单工厂模式
三、程序代码
程序共有七个类：
MyOperation.java
public class MyOperation {
private double numberA;
private double numberB;
public double getNumberA() {
return numberA;
}
public void setNumberA(double numberA) {
this.numberA = numberA;
}
public double getNumberB() {
return numberB;
}
public void setNumberB(double numberB) {
this.numberB = numberB;
} public double getResult() throws Exception {
double result=0;
return result;
}
}OperaAdd.java
public class OperaDiv extends MyOperation{
@Override
public double getResult() throws Exception {
if(this.getNumberB()==0){
throw new Exception("除数不能为0");
}
return this.getNumberA()/this.getNumberB();
}
}OperaSub.java
public class OperaDiv extends MyOperation{
@Override
public double getResult() throws Exception {
if(this.getNumberB()==0){
throw new Exception("除数不能为0");
}
return this.getNumberA()/this.getNumberB();
}
}OperaMul.java
public class OperaDiv extends MyOperation{
@Override
public double getResult() throws Exception {
if(this.getNumberB()==0){
throw new Exception("除数不能为0");
}
return this.getNumberA()/this.getNumberB();
}
}OperaDiv.java
public class OperaDiv extends MyOperation{
@Override
public double getResult() throws Exception {
if(this.getNumberB()==0){
throw new Exception("除数不能为0");
}
return this.getNumberA()/this.getNumberB();
}
}OperationFactory.java
public class OperationFactory {
public static MyOperation createOperation(String operate){
MyOperation operation=null;
switch (operate) {
case "+":
operation=new OperaAdd();
break;
case "-":
operation=new OperaSub();
break;
case "*":
operation=new OperaMul();
break;
case "/":
operation=new OperaDiv();
break;
default:
operation=new MyOperation();
break;
}
return operation;
}
}Calculator.java
import java.util.Scanner;public class Calculator {
/**
* @Title: main
* @Description: 计算器
* @param args
* @return void 返回类型
* @throws
*/
public static void main(String[] args) {
MyOperation operation=null; try {
System.out.println("请输入数字A:"); double numberA=Double.valueOf(new Scanner(System.in).nextLine());
System.out.println("请输入运算符:");
String operaString=new Scanner(System.in).nextLine();
System.out.println("请输入数字B:"); double numberB=Double.valueOf(new Scanner(System.in).nextLine());
operation=OperationFactory.createOperation(operaString);
operation.setNumberA(numberA);
operation.setNumberB(numberB);
System.out.println("结果是："+operation.getResult());
} catch (NumberFormatException e) {
System.out.println("只能输入数字");
} catch (Exception e) {
System.out.println(e.getMessage());
}
}
}