分数类的创建。。。

package com.lovo;

/**
 * 分数类
 * @author 刘顺
 *
 */
public class Rational {
	private int num;		// 分子
	private int den;		// 分母
	
	/**
	 * 构造器
	 * @param num 分子
	 * @param den 分母
	 */
	public Rational(int num, int den) {
		this.num = num;
		this.den = den;
		normalize();
	}
	
	/**
	 * 构造器
	 * @param str 代表一个分数的字符串
	 */
	public Rational(String str) {
		String s1 = str.split("/")[0];	// 分子的字符串
		String s2 = str.split("/")[1];	// 分母的字符串
		this.num = Integer.parseInt(s1);
		this.den = Integer.parseInt(s2);
		normalize();
	}
	
	/**
	 * 构造器
	 * @param x 一个小数
	 */
	public Rational(double x) {
		this.num = (int) (x * 10000);
		this.den = 10000;
		simplify();
		normalize();
	}
	
	/**
	 * public   Rational add(Rational other) { ... }
	 * 访问修饰符  返回类型     方法名(参数列表)       { ... }
	 * 加法
	 * @param other 另一个分数
	 * @return 两个分数相加的结果
	 */
	public Rational add(Rational other) {
		return new Rational(this.num * other.den + this.den * other.num, this.den * other.den).normalize();
	}
	
	/**
	 * 减法
	 * @param other 另一个分数
	 * @return 两个分数相减的结果
	 */
	public Rational sub(Rational other) {
		return new Rational(this.num * other.den - this.den * other.num, this.den * other.den).normalize();
	}
	
	/**
	 * 乘法
	 * @param other 另一个分数
	 * @return 两个分数相乘的结果
	 */
	public Rational mul(Rational other) {
		return new Rational(this.num * other.num, this.den * other.den).normalize();
	}
	
	/**
	 * 除法
	 * @param other 另一个分数
	 * @return 两个分数相除的结果
	 */
	public Rational div(Rational other) {
		return new Rational(this.num * other.den, this.den * other.num).normalize();
	}
	
	/**
	 * 化简
	 * @return 化简后的分数对象
	 */
	public Rational simplify() {
		if(num != 0) {
			int divisor = gcd(Math.abs(num), Math.abs(den));
			num /= divisor;
			den /= divisor;
		}
		return this;
	}
	
	/**
	 * 正规化
	 * @return 正规化以后的分数对象
	 */
	public Rational normalize() {
		if(this.num == 0) {
			this.den = 1;
		}
		else if(this.den < 0) {
			this.den = - this.den;
			this.num = - this.num;
		}
		return this;
	}
	
	public String toString() {
		return num + (den != 1? ("/" + den) : "");
	}
	
	private int gcd(int x, int y) {
		if(x > y) {
			int temp = x;
			x = y;
			y = temp;
		}
		for(int i = x; i > 1; i--) {
			if(x % i == 0 && y % i == 0) {
				return i;
			}
		}
		return 1;
	}
}

package com.lovo;
/**

*    主程序

*   只调用了其中部分方法

*/
import java.util.Scanner;

public class Test04 {

	public static void main(String[] args) {		
		Scanner sc = new Scanner(System.in);
		System.out.print("r1 = ");
		String str1 = sc.next();
		Rational r2 = new Rational(0.3);
		
		Rational r1 = new Rational(str1);
		
		System.out.printf("%s + %s = %s\n", r1, r2, r1.add(r2).simplify());
		System.out.printf("%s - %s = %s\n", r1, r2, r1.sub(r2).simplify());
		System.out.printf("%s * %s = %s\n", r1, r2, r1.mul(r2).simplify());
		System.out.printf("%s / %s = %s\n", r1, r2, r1.div(r2).simplify());
		
		sc.close();
	}
}