设计模式之简单工厂模式

简单工厂模式，也叫静态工厂模式，即由一个静态工厂类来统一创建所需要的实例对象。

本例中，将主要实现加减乘除计算。

第一步，定义抽象基类Operation

/**
 * @author abo
 * @title Operation
 * @ProjectName Test
 * @Description: 运算类的基类，定义了两个运算数
 * @CreateDate 2018-10-13 14:15
 */
public abstract  class Operation {
    private double numberA=0;
    private double numberB=0;

    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 abstract double getResult();
}

第二步：定义加减乘除四个子类继承于Operation类

OperationAdd(加法运算子类)

/**
 * @author abo
 * @title OperationAdd
 * @ProjectName Test
 * @Description: 继承操作类，实现加法运算
 * @CreateDate 2018-10-13 14:17
 */
public class OperationAdd extends Operation {

    @Override
    public double getResult() {
        double result = 0;
        result = getNumberA()+getNumberB();
        return result;
    }
}

OperationSub(减法运算子类)

/**
 * @author abo
 * @title OperationSub
 * @ProjectName Test
 * @Description: 继承操作类，实现减法运算
 * @CreateDate 2018-10-13 14:22
 */
public class OperationSub extends Operation {
    @Override
    public double getResult() {
        double result = 0;
        result = getNumberA()-getNumberB();
        return result;
    }
}

OperationMul(乘法运算子类)

/**
 * @author abo
 * @title OperationMul
 * @ProjectName Test
 * @Description: 继承操作类，实现乘法运算
 * @CreateDate 2018-10-13 14:23
 */
public class OperationMul extends Operation {
    @Override
    public double getResult() {
        double result= 0;
        result = getNumberA()*getNumberB();
        return result;
    }
}

OperationDiv(除法运算子类)

/**
 * @author abo
 * @title OperationDiv
 * @ProjectName Test
 * @Description: 继承操作类，实现除法运算
 * @CreateDate 2018-10-13 14:24
 */
public class OperationDiv extends Operation {
    @Override
    public double getResult() {
        double result=0;
        result = getNumberA()/getNumberB();
        return result;
    }
}

OperationFactory(运算工厂类)

/**
 * @author abo
 * @title OperationFactory
 * @ProjectName Test
 * @Description: 简单运算工厂类，用于创建操作类对象
 * @CreateDate 2018-10-13 14:26
 */
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;
    }
}

客户端程序Test类

        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入第一个数字：");
        double numberA = scanner.nextDouble();
        System.out.println("请输入第二个数字：");
        double numberB = scanner.nextDouble();
        System.out.println("请输入操作符：如+、-、*、/");
        String operator = scanner.next();
        try {
            Operation oper;
            oper = OperationFactory.createOperate(operator);
            oper.setNumberA(200);
            oper.setNumberB(4);
            System.out.println("结果为："+oper.getResult());
        } catch (Exception e) {
            e.printStackTrace();
            System.out.println("运算结果出错！");
        }