JAVA互评—有理数类的设计

1.相关代码

• 有理数类代码

package rational;

public class Rational{
	
	private int numerator;					//分子
	private int denominator;				//分母
	
	private int getGcd(int nrt,int dmt) {	//获取最大公约数
		int max;
		int min;
		int flag=0;
		if(nrt<0&&dmt<0)flag=1;
		nrt=Math.abs(nrt);
		dmt=Math.abs(dmt);

		if(nrt>dmt) {
			max=nrt;
			min=dmt;
		}else {
			max=dmt;
			min=nrt;
		}

		if(min==0)return 1;
		int r= max % min;
		while(r>0) {							//辗转相除法
			max=min;
			min=r;
			r=max%min;
		}
		if(flag==1)return -min;
		return min;
	}
	
	public static Rational abs(Rational x) {	//取绝对值
		Rational a=new Rational(0,1);
		a.denominator=x.denominator;
		a.numerator=x.numerator;
		if(a.denominator<0)a.denominator*=-1;
		if(a.numerator<0)a.numerator*=-1;
		
		return a;
	}
	
	public Rational(int nrt,int dmt) {			//两个整型的构造函数
		this.numerator=nrt;
		this.denominator=dmt;
		if(dmt==0) {
			System.out.println("Error In Denominator 0!");
			System.exit(0);
		}else if(nrt==0) {
			this.numerator=0;
			this.denominator=1;
		}
		int x=getGcd(nrt,dmt);
		if(x>=1||-x>=1) {
			this.numerator/=x;
			this.denominator/=x;
		}
	}
	
	
	
	public Rational(Double x) {					//一个Double构造函数
		String s=x.toString();
		int index=s.indexOf(".");
		int dmt=s.length()-index;
		dmt=(int) Math.pow(10, dmt);
		int nrt=(int) (x*dmt);
		int k=getGcd(dmt,nrt);
		if(k>=1||-k>=1) {
			this.numerator=nrt/=k;
			this.denominator=dmt/=k;
		}
	}
	
	
	
	public Rational(String s) {					//String构造函数
		Double x=Double.parseDouble(s);    
		int index = s.indexOf(".");
		if(index==-1) {
			this.numerator=Integer.parseInt(s);
			this.denominator=1;
			return;
		}
		int dmt=s.length()-index;
		dmt=(int) Math.pow(10, dmt);
		int nrt=(int) (x*dmt);
		int k=getGcd(nrt,dmt);
		if(k>=1||-k>=1) {
			this.numerator=nrt/=k;
			this.denominator=dmt/=k;
		}
	}
	
	public Rational plus(Rational x) {			//加法
			
		int nrt=this.numerator*x.denominator+this.denominator*x.numerator;
		int dmt=this.denominator*x.denominator;
		
		Rational a =new Rational(nrt,dmt);
		return a;
	}
	
	public Rational minus(Rational x) {		//减法
		
		int nrt=this.numerator*x.denominator-this.denominator*x.numerator;
		int dmt=this.denominator*x.denominator;
		
		Rational a =new Rational(nrt,dmt);
		return a;
	}
	
	public Rational multiply(Rational x) {			//乘法
		
		int nrt=this.numerator*x.numerator;
		int dmt=this.denominator*x.denominator;
		
		Rational a =new Rational(nrt,dmt);
		return a;
	}
	
	public Rational divide(Rational x) {		//除法
		
		int nrt=this.numerator*x.denominator;
		int dmt=this.denominator*x.numerator;
		
		Rational a =new Rational(nrt,dmt);
		return a;
	}
	
	public String toString() {					//返回有理数的字符串形式
		Rational x=new Rational(0,1);
		String s=new String();
		x.denominator=this.denominator;
		x.numerator=this.numerator;
		if(x.denominator*x.numerator<0) {
			s+="-";
			x=Rational.abs(x);
		}
		if (x.denominator == 1)s+=x.numerator;
		else s+=x.numerator + "/" + x.denominator;
		return s;
	}
	
	public boolean equals(Rational x) {				//判断两数是否相等
		if(this.minus(x).toString().equals("0"))return true;
		return false;
	}
	
	public Rational compareTo (Rational x) {		//返回两数中较大的数
		int index=this.minus(x).toString().indexOf("-");
		if(index==-1) {
			return this;
		}else {
			return x;
		}
		
	}
	
}

• 调用代码

import rational.Rational;
public class Main{    
    public static void main(String args[]){
    	int x = 1;
    	int y = -1;
    	Double x1=-1.3;
    	String s= "-2.5";
    	
    	Rational a= new Rational(x,y);
    	Rational b= new Rational(x1);
    	Rational c= new Rational(s);
    	Rational d= new Rational(-5,2);
    	
    	System.out.println(x+"/"+y+" to Rational is :"+a.toString());
    	System.out.println(x1+" to Rational is :"+b.toString());
    	System.out.println(s+" to Rational is :"+c.toString());
    	System.out.println();
    	
    	System.out.println(b.toString()+" equals "+c.toString()+" ? : "+b.equals(c));
    	System.out.println(c.toString()+" equals "+d.toString()+" ? : "+c.equals(d));
    	System.out.println("bigger in "+b.toString()+" and "+c.toString()+" : "+b.compareTo(c).toString());
    	System.out.println(b.toString()+" to abs : "+Rational.abs(b));
    	System.out.println();
    	
    	System.out.println(b.toString()+" + "+c.toString()+" : "+b.plus(c).toString());
    	System.out.println(b.toString()+" - "+c.toString()+" : "+b.minus(c).toString());
    	System.out.println(b.toString()+" * "+c.toString()+" : "+b.multiply(c).toString());
    	System.out.println(b.toString()+" / "+c.toString()+" : "+b.divide(c).toString());
    }
}

2.测试数据及结果

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语言侧重与过程，java中的类更侧重对象的操作。例如a+b，C语言中是plus(a,b);而在java中则是a.plus(b);具体指向了是a这个对象进行加法运算。
• java类中的方法是针对这个类中的对象，而C语言的函数并没有明确规定，只需传参符合即可。

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?
答：直接导入rational包即可使用。
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?
答：依赖，因为我的有理数类属性中仅有分子跟分母，且当修改该属性后，代码可能报错，会影响他人使用。
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?
答：public方法中有加、减、乘、除、toString()、equals()、cpmpareTo()和取绝对值abs()，设置合适；private方法中仅有取最大公约数getGcd()，当不想外界调用时设置为private方法。