Java程序设计-有理数类的设计

1.有理数类代码：

public class RationalNum {
	private int numerator = 0;
	private int denominator = 1;

	public int getnumerator() {
		return numerator;
	}

	public int getdenominator() {
		return denominator;
	}

	public RationalNum() {
		this.numerator = 0;
		this.denominator = 1;
	}

	public RationalNum(int numerator, int denominator) { // 以分子分母形式构造
		if (denominator == 0) {
			System.out.println("Denominator cannot be zero!");
			System.exit(1);
		} else if (numerator == 0) {
			this.numerator = 0;
			this.denominator = 1;
		}
		int gcd = GCD(numerator, denominator);
		this.numerator = numerator / gcd;
		this.denominator = denominator / gcd;
	}

	public int GCD(int num1, int num2) {               // 辗转相除法获取最大公约数
		if (num1 < num2) {
			int k = 0;
			k = num1;
			num1 = num2;
			num2 = k;
		}
		return num1 % num2 == 0 ? num2 : GCD(num2, num1 % num2);
	}

	public RationalNum(Double num) {                  // 输入小数形式构造
		String str = num.toString();
		int index = str.indexOf('.');
		int den = (int) Math.pow(10, str.length() - index);
		int nrt = (int) (num * den);
		int gcd = 0;
		if (nrt < 0) {
			gcd = GCD(-nrt, den);
		} else {
			gcd = GCD(nrt, den);
		}
		this.numerator = nrt / gcd;
		this.denominator = den / gcd;
	}

	public RationalNum(String str) {                 // 输入字符串构造
		Double num = Double.parseDouble(str);
		int index = str.indexOf('.');
		if (index == -1) {
			this.numerator = Integer.parseInt(str);
			this.denominator = 1;
			return;
		}
		int den = (int) Math.pow(10, str.length() - index);
		int nrt = (int) (num * den);
		int gcd = 0;
		if (nrt < 0) {
			gcd = GCD(-nrt, den);
		} else {
			gcd = GCD(nrt, den);
		}
		this.numerator = nrt / gcd;
		this.denominator = den / gcd;
	}

	public RationalNum add(RationalNum a) {          //加法
		int nrt = a.numerator * this.denominator + a.denominator * this.numerator;
		int den = a.denominator * this.denominator;
		RationalNum num = new RationalNum(nrt, den);
		return num;
	}

	public RationalNum minus(RationalNum a) {        //减法
		int nrt = this.numerator * a.denominator - a.numerator * this.denominator;
		int den = a.denominator * this.denominator;
		RationalNum num = new RationalNum(nrt, den);
		return num;
	}

	public RationalNum mulitply(RationalNum a) {    //乘法
		int nrt = this.numerator * a.numerator;
		int den = this.denominator * a.denominator;
		RationalNum num = new RationalNum(nrt, den);
		return num;
	}

	public RationalNum divide(RationalNum a) {      //除法
		int nrt = this.numerator * a.denominator;
		int den = this.denominator * a.numerator;
		RationalNum num = new RationalNum(nrt, den);
		return num;
	}

	public RationalNum abs() {                      //求绝对值
		int nrt=0,den=1;
		if(this.numerator<0) {
			nrt=-this.numerator;
		}
		if(this.denominator<0) {
			den=-this.denominator;
		}
		RationalNum num=new RationalNum(nrt,den);
		return num;
	}
	 
	public boolean equals(RationalNum a) {         //比较两个数是否相等
		if(this.divide(a).toString().equals("1")) return true;
		else return false;
	}

        public RationalNum returnLargerNum(RationalNum a) {     //返回两个数中较大的数
    	       RationalNum num =new RationalNum(0,1);
    	       num=this.minus(a);
    	      if(num.intValue()<0)
    	      {
    		   return a;
    	      }
    	      else {
    		   return this;
    	      }
        }
    
        public int intValue() {			              //转化为int类型
		return (int) this.numerator / this.denominator;
	}

}

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2.测试代码

package Main;
import rational.RationalNum;
public class Main {

	public static void main(String[] args) {
		int x1=-2,y1=5;
		int x2=3,y2=7;
		double x=3.4;
		int n=3,m=0;
		String num="66.66";
		
		RationalNum a=new RationalNum(x1,y1);   //-2/5
		RationalNum b=new RationalNum(x2,y2);   //3/7
		RationalNum c=new RationalNum(x);
		RationalNum d=new RationalNum(num);	
		
		System.out.println("a="+a.toString()+" ; "+"b="+b.toString()+" ; "+"c="+c.toString()+" ; "+"d="+d.toString());
		System.out.println("a + b = "+a.add(b).toString());
		System.out.println("a - b = "+a.minus(b).toString());
		System.out.println("a * b = "+a.mulitply(b).toString());
		System.out.println("a / b = "+a.divide(b).toString());
		System.out.println("Absolute value of a = "+a.abs().toString());
		System.out.println("The nth power of a = "+a.pow(a, n));
		System.out.println("The int type of a is "+a.intValue());
		System.out.println("The double type of a is "+a.doubleValue());
		System.out.println("The larger number of "+a.toString()+" and "+b.toString()+" is "+a.returnLargerNum(b));
		System.out.println("Is "+a.toString()+" and "+b.toString()+" the same? "+a.equals(b));
	}

}

测试结果：

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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语言强调的是过程，在写代码是更侧重函数的设计编写来实现过程，而在JAVA中强调的是根据对象属性和目标来编写代码，如何让属性间相互联系，如何更好封装是考虑的重点。

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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。

<1>别人如何复用你的代码？

• 通过import关键字导入包rational中的类RationalNum。

<2>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？

• (1)是。(2)是，当我将类中方法的入参修改后，其他人想要用这个类也要做出相应修改。

<3>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？

• (1)合适，因为这样方便复用，而且在别的包也能调用。(2)有的方法（例如GCD）设置成private是因为获取最大公约数一般在化简分数时才有较大用处，外界一般不需要调用。