Java学习--面向对象2：有理数加减乘除的实现

分数加减乘除案例

本案例是为了帮助我们更加深刻到了解面向对象，直接上代码：

分数类

package com.mfs.test;

public class FractionalNumber {

	public int numerator; // 分子
	public int denominator; // 分母

	public FractionalNumber(int numerator, int denominator) {
		if (numerator == 0) {
			this.numerator = numerator;
			this.denominator = denominator;
		} 
		else {
			int com = maxCom(Math.abs(numerator), Math.abs(denominator));//求最大公约数
			if (denominator < 0) {
				numerator = -numerator;
				denominator = -denominator;
			}
			this.numerator = numerator / 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 FractionalNumber add(int numerator, int denominator) {// 加
		int d = denominator;
		denominator = this.denominator * denominator;
		numerator = this.numerator * d + numerator * this.denominator;
		
		return new FractionalNumber(numerator, denominator);
	}

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

	public FractionalNumber mul(int numerator, int denominator) {// 乘
		
		denominator = this.denominator * denominator;
		numerator = this.numerator * numerator;

		return new FractionalNumber(numerator, denominator);
	}

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

		return new FractionalNumber(numerator, denominator);
	}

	@Override
	public String toString() {
		return numerator + "/" + denominator;
	}

}

main方法，测试类

package com.mfs.test;

import java.util.Scanner;

public class test {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		
		String str = sc.next();//读取输入的算式
		
		
		int a = Integer.parseInt(str.charAt(0)+"");//获得两个分数的分子分母，考虑到项目的复杂性，
		int b = Integer.parseInt(str.charAt(2)+"");//输入的算式各项只能是正的，并且分子分母只能一位
		int c = Integer.parseInt(str.charAt(4)+"");
		int d = Integer.parseInt(str.charAt(6)+"");
		
		FractionalNumber f1 = new FractionalNumber(a, b);
		
		switch(str.charAt(3)) {
		case '+': System.out.println(f1.add(c, d).toString());
		break;
		case '-':System.out.println(f1.sub(c, d).toString());
		break;
		case '*':System.out.println(f1.mul(c, d).toString());
		break;
		case '/':System.out.println(f1.div(c, d).toString());
		break;
		}
	}

}