设计模式最简Demo：简单工厂模式[Simple Factory Pattern]

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1. 程序需求

实现一个计算器程序，要求能实现加减乘除等常用操作，且扩展性强。

2. UML图

这里写图片描述

3. Java实现

Operation

package simple_factory_pattern;public abstract class Operation {    protected double numberA;    protected double numberB;    public abstract double getResult();}

OperationAdd

package simple_factory_pattern;public class OperationAdd extends Operation {    @Override    public double getResult() {        return numberA + numberB;    }}

OperationSub

package simple_factory_pattern;public class OperationSub extends Operation {    @Override    public double getResult() {        return numberA - numberB;    }}

OperationMul

package simple_factory_pattern;public class OperationMul extends Operation {    @Override    public double getResult() {        return numberA * numberB;    }}

OperationDiv

package simple_factory_pattern;public class OperationDiv extends Operation {    @Override    public double getResult() {        return numberA / numberB;    }}

OperationFactory

package simple_factory_pattern;public class OperationFactory {    public static Operation createOperate(String operate){        Operation operation = null;        switch (operate){            case "+":                operation = new OperationAdd();                break;            case "-":                operation = new OperationSub();                break;            case "*":                operation = new OperationMul();                break;            case "/":                operation = new OperationDiv();                break;        }        return operation;    }}

Test

package simple_factory_pattern;public class Test {    public static void main(String[] args) {        String input = "+";        Operation operation = OperationFactory.createOperate(input);        operation.numberA = 2.1;        operation.numberB = 2.2;        System.out.println(operation.getResult());    }}

4. 总结

继承、封装、多态，可扩展。

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