一、简单工厂模式

• 可维护
• 可复用
• 可扩展
• 灵活性好

工厂: 用一个单独的类来做创造实例的过程。

简单运算工厂类：

package SimpleFactory;

public class OperFactory {

    public static Operation createOperate(char operate)
    {
        Operation oper = null;
        switch(operate)
        {
        case '+':
            oper = new OperAdd();
            break;
        case '-':
            oper = new OperSub();
            break;
        case '*':
            oper = new OperMul();
            break;
        case '/':
            oper = new OperDiv();
            break;
        }
        return oper;
    }

}

父类：Operation

package SimpleFactory;

public class Operation {

    protected int numA ;
    protected int numB ;


    public int getNumA() {
        return numA;
    }


    public void setNumA(int numA) {
        this.numA = numA;
    }


    public int getNumB() {
        return numB;
    }


    public void setNumB(int numB) {
        this.numB = numB;
    }


    public int GetResult()
    {
        return 0;
    }

}

具体的操作类：

package SimpleFactory;

public class OperAdd extends Operation{

    public int GetResult()
    {
        int result = 0;
        result = numA + numB;
        return result;
    }

}

package SimpleFactory;

public class OperSub extends Operation{

    public int GetResult()
    {
        int result = 0;
        result = numA - numB;
        return result;
    }
}

package SimpleFactory;

public class OperMul extends Operation{

    public int GetResult()
    {
        int result = 0;
        result = numA * numB;
        return result;
    }
}

package SimpleFactory;

public class OperDiv extends Operation{

    public int GetResult()
    {
        int result = 0;
        if(numB == 0)
            try {
                throw new Exception("0!!!");
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        result = numA / numB;
        return result;
    }
}

主程序：

package SimpleFactory;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Scanner;

public class Program {

    public static void main(String[] args) throws IOException
    {
        try
        {
            Scanner sc = new Scanner(System.in);
            Operation oper;

            System.out.println("please input number A :");
            String strNumA = sc.nextLine();
            System.out.println("please input mark :");
            char strOperate = sc.nextLine().charAt(0);
            System.out.println("please input number B :");
            String strNumB = sc.nextLine();
            oper = OperFactory.createOperate(strOperate);
            oper.numA = Integer.valueOf(strNumA);
            oper.numB = Integer.valueOf(strNumB);

            System.out.println("the two nums are: " + Integer.valueOf(strNumA) + "and" + 
                    Integer.valueOf(strNumB) + " while the mark is \"" + strOperate +"\"");
            int strResult = 0;

            strResult = oper.GetResult();

            System.out.println("the result is : " + strResult);
        }
        catch(Exception ex)
        {
            System.out.println("you have something wrong : " + ex.getMessage());
        }
    }

}