Java程序设计作业01

Java程序设计作业01 - 有理数类的设计

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1.给出你的有理数类代码

package rationalnumber;

public class Rational {
	private int numerator;      //分子
	private int denominator;	//分母
	
	public int getNumerator() {		//获取分子
		return numerator;
	}

	public int getDenominator() {		//获取分母
		return denominator;
	}
	
	public Rational() {			//默认构造
		this.numerator = 0;
		this.denominator = 1;
	}

        public Rational(int x) {                 //只有整数时构造有理数
                if(x < 0) {
                        this.numerator = -x;
                        this.denominator = -1;
                }else {
                        this.numerator = x;
                        this.denominator = 1;
                }
        }

	public Rational(int numerator, int denominator) {		//以分子、分母形式构造有理数
		if(denominator == 0) {
			System.out.println("分母不能为零！");
			System.exit(1);
		}else if(numerator == 0){
			this.numerator = 0;
			this.denominator = 1;
			return;
		}
		int gcd = getGCD(numerator, denominator);
		
		this.numerator = numerator / gcd;
		this.denominator = denominator / gcd;
	}
	
	public Rational(Double x) {			//直接输入小数时构造有理数
		int flag = 0;
		if(x < 0) {
			flag = 1;
			x = -x;
		}
		String s = x.toString();
		String[] str = new String[2];
		str = s.split("\.");
		
		int num = (int) (Integer.parseInt(str[0]) * Math.pow(10, str[1].length()) + Integer.parseInt(str[1]));
		int den = (int) Math.pow(10, str[1].length());
		if(flag == 1)
			den = -den;
		int gcd = getGCD(num, den);
		
		this.numerator = num / gcd;
		this.denominator = den / gcd;
	}
	
	private int getGCD(int a, int b) {		//获取最大公约数，用于化简分式
		int t = 0;
		if(a < b) {
			t = a;
			a = b;
			b = t;
		}
		t = a % b;
		while(t != 0) {
			a = b;
			b = t;
			t = a % b;
		}
		return b;
	}
	
	public Rational add(Rational a) {			//相加
		int num = a.numerator * this.denominator + a.denominator * this.numerator;
		int den = a.denominator * this.denominator;
		
		Rational r = new Rational(num, den);
		return r;
	}
	
	public Rational minus(Rational a) {			//相减
		int num = this.numerator * a.denominator - this.denominator * a.numerator;
		int den = a.denominator * this.denominator;
		
		Rational r = new Rational(num, den);
		return r;
	}
	
	public Rational mulitply(Rational a) {		//相乘
		int num = a.numerator * this.numerator;
		int den = a.denominator * this.denominator;
		
		Rational r = new Rational(num, den);
		return r;
	}
	
	public Rational divide(Rational a) {		//相除
		int num = a.numerator * this.denominator;
		int den = a.denominator * this.numerator;
		
		Rational r = new Rational(num, den);
		return r;
	}
	
	public Rational abs() {			//取绝对值
		int num = (this.numerator < 0 ? this.numerator : -this.numerator);
		int den = (this.denominator < 0 ? this.denominator : -this.denominator);
		
		Rational r = new Rational(num, den);
		return r;
	}
	
	public Rational pow(Rational a, int n) {		//取有理数a的n次方
		int num = a.numerator;
		int den = a.denominator;
		for(int i = 1; i < n; i++) {
			num = num * a.numerator;
			den = den * a.denominator;
		}
		
		Rational r = new Rational(num, den);
		return r;
	}
	
	public Rational remainder(Rational a) {			//取余
		if(this.divide(a).denominator == 1)
			return new Rational(0, 1);
		
		Rational r = new Rational();
		int x = this.divide(a).numerator / this.divide(a).denominator + 1;
		r = this.minus((new Rational(x, 1)).mulitply(a));
		return r;
	}
	
	public int compareTo(Rational a) {		//比较两个有理数的大小，
		int x = this.numerator * a.denominator;
		int y = a.numerator * this.denominator;
		
		if(x > y) {				//-1、0、1分别代表左边小于、等于、大于右边
			return 1;
		}else if(x < y) {
			return -1;
		}else {
			return 0;
		}
	}
	
	public int signum() {		//返回有理数的正负符号
		if(this.denominator < 0)
			return -1;
		return 1;
	}
	
	public int intValue() {			//转化为int类型
		return (int) this.numerator / this.denominator;
	}
	
	public float floatValue(){		//转化为float类型（其余类型代码类似，故不重复）
		return (float) this.numerator / this.denominator;
	}
	
	public String toString() {		//将有理数转化成分数的字符串形式
		if(this.numerator == 0) {
			return "0";
		}else if(this.denominator == 1){
			return this.numerator + "";
		}else {
			String s = "(" + ((double) this.numerator / this.denominator) + ")";
			return this.numerator + "/" + this.denominator + s;
		}
	}

}

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2.给出你的测试代码

import java.util.Scanner;

import rationalnumber.Rational;

public class Main {

	public static void main(String[] args)  {
		//Scanner sc = new Scanner(System.in);
		Rational r1 = new Rational(1, 2);
		Rational r2 = new Rational(0.4);
		Rational r = new Rational();
		
		System.out.println("r1 = " + r1.toString() + " ; " + "r2 = " + r2.toString());
		
		System.out.println("r1 + r2 = " + r1.add(r2).toString());
		System.out.println("r1 - r2 = " + r1.minus(r2).toString());
		System.out.println("r1 * r2 = " + r1.mulitply(r2).toString());
		System.out.println("r1 / r2 = " + r1.divide(r2).toString());
		System.out.println("abs(r1) = " + r1.abs().toString());
		System.out.println("(r1)^2 = " + r.pow(r1, 2).toString());
		System.out.println("r1 % r2 = " + r1.remainder(r2).toString());
		System.out.println("r1 compare to r1 = " + r1.compareTo(r2));
		System.out.println("r1's signum = " + r1.signum());
		System.out.println("r1 to Integer = " + r1.intValue());
	}
}

测试结果图：
（1）r1 = Rational(1,2); r2 = Rational(0.4)

（2）r1 = Rational(-1,1); r2 = Rational(-1.6)

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3.类名、变量名命名需符合Java规范

• 包名全部小写、类名首字母大写、变量名命名使用驼峰法。

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4.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语言的代码在编写过程中更偏向于过程，所以在设计过程中会更偏向于函数的设计。在Java类的设计中我们会更注重于类的方法和属性的编写，该如何让这些东西联系在一起、如何封装则是考虑的重点，并且与C语言相比，Java重载函数的特性让它更突出面向对象的特点，例如在该作业中通过不同的方式初始化构造有理数。

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5.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。

• 别人如何复用你的代码？
  可以导入我所写的rationalnumber包中的有理数类，就可以使用该类中的内容了。

• 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？
  别人的代码依赖我的有理数类的属性。当我的有理数类的属性修改时，比如将int改成double类型时会影响到他人调用代码。（其实我没看懂这题的意思）

• 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？
  合适，因为其中的大部分方法我希望他们能在包外也能够调用，有的方法设置成private可以将方法限制于该类中访问，例如在本作业中的用于化简分数的获取最大公约数函数getGCD，我只想它用于新的有理数化简，而不希望其他调用，因此设计成了private方法。