有理数类的设计

1.有理数类的代码

import java.util.Scanner;

public class Rational {

	private int numberator=0;
	private int denominator=1;
	

	public Rational() {
		this(0,1);
	}
	
	public Rational(int numberator,int denominator) {     
    	
		if (numberator == 0) {
			this.numberator = numberator;
			this.denominator = denominator;
		} 
		else {
			int com = maxCom(Math.abs(numberator), Math.abs(denominator));//求最大公约数
			if (denominator < 0) {
				numberator = -numberator;
				denominator = -denominator;
			}
			this.numberator = numberator / com;
			this.denominator = denominator / com;
		}
    }
	
	private int maxCom(int a, int b) { // 求最大公约数
		if (a < b) {
			int c = a;
			a = b;
			b = c;
		}
		int r = 0;
		try {
			r = a % b;

		} catch (Exception e) {
			System.out.println(e.getMessage());
		} // 分母为零时异常处理
		while (r != 0) {
			a = b;
			b = r;
			r = a % b;
		}

		return b;
	}
	
	public Rational add(int numberator,int denominator) {
		int d = denominator;
		denominator = this.denominator * denominator;
		numberator = this.numberator * d + numberator * this.denominator;
		
		return new Rational(numberator, denominator);

	}
	public Rational sub(int numberator, int denominator) {// 减
		int d = denominator;
		denominator = this.denominator * denominator;
		numberator = this.numberator * d - numberator * this.denominator;
		
		return new Rational(numberator, denominator);
	}

	public Rational mul(int numberator, int denominator) {// 乘
		
		denominator = this.denominator * denominator;
		numberator = this.numberator * numberator;

		return new Rational(numberator, denominator);
	}

	public FractionalNumber div(int numberator, int denominator) {// 除
		int d = denominator;
		denominator = this.denominator * numberator;
		numberator = this.numberator * d;

		return new FractionalNumber(numberator, denominator);
	}
	
	public String toString() {
		return numberator + "/" + denominator;
	}

2.测试代码

public static void main (String[] args) {
		{
			System.out.println("请输入要计算的表达式：");
			Scanner sc=new Scanner(System.in);
			String str=sc.next();
			int a=Integer.parseInt(str.charAt(0)+"");//分子
			int b=Integer.parseInt(str.charAt(2)+"");//分母
			int c=Integer.parseInt(str.charAt(4)+"");
			int d=Integer.parseInt(str.charAt(6)+"");
			
			Rational num=new Rational(a,b);
			
			switch(str.charAt(3)) {
			case'+':System.out.println("加法");
				System.out.println(num.add(c,d).toString());
			//break;测试代码
			case'-':System.out.println("减法");
				System.out.println(num.sub(c,d).toString());
			//break;
			case'*':System.out.println("乘法");
				System.out.println(num.mul(c,d).toString());
			//break;
			case'/':System.out.println("除法");
				System.out.println(num.div(c,d).toString());
			//break;
			}
}}
}

3.尝试描述怎么与c语言的有理数代码相比较,为什么你设计的类更加面向对象?

c语言的有理数代码，我会倾向于从过程考虑，考虑要写怎样的函数来用它，而不是考虑它应该会有怎样的方法.

4.尝试从代码复用的角度来描述你设计的有理数类。从几个方面讨论。

a.别人如何复用你的代码?
导入我书写的类的包，就可以使用我写的类和方法

b.别人的代码是否依赖你的有理数类的属性?当你的有理数类的属性修改时,是否会影响他人调用你有理数类的代码?
依赖，我的有理数类的为private，所以不会影响他人调用我的有理数代码

c.有理数类的public方法是否设置合适?为什么有的方法设置为private?
适合