简单工厂——实现四则运算

实质：
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。

过程：
1.合理输入两个数字
2.合理输入一个运算符（正则）
3.工厂创建具体类 （赋给成员）
4.成员执行计算函数

代码

package Try_sig.Fac;

import java.util.Arrays;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


public class Alu_fac {
	public static void main(String[] args) {
		Result result = new Result();
		input_2_num(result);
		input_oper(result);
		Fac_M factoc = new Fac_M(result);
		factoc.get_End();
	}

	public static void input_2_num(Result result) {
		String a = null;
		String b = null;
		Scanner input = new Scanner(System.in);
		System.out.println("----start-----");
		double d_a = 0;
		double d_b = 0;

		boolean a_flag = true;
		while (a_flag) {
			try {
				System.out.print("input number a :");
				a = input.nextLine();
				d_a = Double.parseDouble(a);
				a_flag = false;
			} catch (Exception e) {
				continue;
			}
		}

		boolean b_flag = true;
		while (b_flag) {
			try {
				System.out.print("input number b :");
				b = input.nextLine();
				d_b = Double.parseDouble(b);
				b_flag = false;
			} catch (Exception e) {
				continue;
			}
		}

		result.a = d_a;
		result.b = d_b;
	}

	public static void input_oper(Result result) {
		Scanner input = new Scanner(System.in);
		boolean bool_op = true;
		String in_str = null;
		Pattern pattern;
		Matcher matcher;
		String[] regex = { "[+]", "[-]", "[*]", "[/]" };
		int index = 0;

		while (bool_op) {
			System.out.print("输入运算符(+-*/)  : ");
			in_str = input.nextLine();
			for (int i = 0; i < 4; i++) {
				pattern = Pattern.compile(regex[i]);
				matcher = pattern.matcher(in_str);
				if (matcher.matches()) {
					bool_op = false;
					index = i;
					break;
				}
			}
		}
		result.op = regex[index].charAt(1) + "";

	}
}

class Result {
	public static double a = 0;
	public static double b = 0;
	public static String op = null;
}

abstract class Opera_abstract {
	public abstract double getEnd();
}

class Opera_add extends Opera_abstract {
	private double end_num = 0;

	public Opera_add(Result result) {
		end_num = result.a + result.b;
	}

	@Override
	public double getEnd() {
		return end_num;
	}
}

class Opera_sub extends Opera_abstract {
	private double end_num = 0;

	public Opera_sub(Result result) {
		end_num = result.a - result.b;
	}

	@Override
	public double getEnd() {
		return end_num;
	}
}

class Opera_mul extends Opera_abstract {
	private double end_num = 0;

	public Opera_mul(Result result) {
		end_num = result.a * result.b;
	}

	@Override
	public double getEnd() {
		return end_num;
	}
}

class Opera_div extends Opera_abstract {
	private double end_num = 0;

	public Opera_div(Result result) {
		end_num = result.a / result.b;
	}

	@Override
	public double getEnd() {
		return end_num;
	}
}

class Fac_M {
	private static Result result = null;
	private static Opera_abstract op = null;
	public Fac_M(Result result) {
		this.result = result;
		switch (this.result.op) {
		case "+":
			op = new Opera_add(result);
			break;
		case "-":
			op = new Opera_sub(result);
			break;
		case "*":
			op = new Opera_mul(result);
			break;
		case "/":
			op = new Opera_div(result);
			break;
		} 
	}

	public void get_End() {
		System.out.println("运算结果： a"+result.op+"b = "+op.getEnd());
	}
	
}