工厂方法

一、定义：

工厂方法模式，定义一个用于创建对象的接口，让子类决定实例化哪个类。工厂方法使一个类的实例化延迟到其子类。

二、示例代码：

//工厂接口，通过实现工厂接口，才创建对应的实例
public interface IFactory {
    public Operator createOperator();
}
//加法工厂
public class AddFactory implements IFactory{
    @Override
    public Operator createOperator() {
        return new Addition();
    }
}
//除法工厂
public class DivisionFactory implements IFactory {
    @Override
    public Operator createOperator() {
        return new Division();
    }
}
//乘法工厂
public class MultipleFactory implements IFactory{
    @Override
    public Operator createOperator() {
        return new Multiplication();
    }
}
//减法工厂
public class SubFactory implements IFactory {
    @Override
    public Operator createOperator() {
        return new Subtraction();
    }
}
//工厂方法所创建对象的父类
public abstract class Operator {
    private String numberA;
    private String numberB;

    String printResult;

    public String getNumberA() {
        return numberA;
    }

    public String getNumberB() {
        return numberB;
    }

    public void setNumberA(String numberA) {
        this.numberA = numberA;
    }

    public void setNumberB(String numberB) {
        this.numberB = numberB;
    }

    public abstract String getResult(String operator);
}
//加法运算类
public class Addition extends Operator {

    public String getResult(String operator) {
        DateFormat.getDateInstance();
        Double result=Double.parseDouble(getNumberA())+Double.parseDouble(getNumberB());
        printResult=result.toString();
        return printResult;

    }
}
//除法运算类
public class Division extends Operator {
    public String getResult(String operator) {
        if (StringUtils.equals(getNumberB(),"0")){
            printResult="除数不能为零0";
        }
        else {
        Integer result = (int) (Double.parseDouble(getNumberA()) / Double.parseDouble(getNumberB()));
        printResult = result.toString();
        }
        return printResult;
    }
}
//乘法运算类
public class Multiplication extends Operator {

    public String  getResult(String operator){
        Double result=Double.parseDouble(getNumberA())*Double.parseDouble(getNumberB());
        printResult=result.toString();
        return printResult;
    }

}
//减法运算类
public class Subtraction extends Operator {
    public String getResult(String operator) {
        Double result = Double.parseDouble(getNumberA()) - Double.parseDouble(getNumberB());
        printResult = result.toString();
        return printResult;
    }
}
//客户端
public class Client {
    public static void main(String[] args) throws Exception {
        String numberA="23";
        String numberB="2";
        String opt="2";
        /*利用工厂生成实例*/
        IFactory factory=new MultipleFactory();
        Operator operator = factory.createOperator();
        operator.setNumberA(numberA);
        operator.setNumberB(numberB);
        String result =operator.getResult(opt);
        System.out.println(result);

    }
}