• CS61b lab2 打卡


    修改后的代码:

    import java.io.*;
    
        /** The Fraction class implements nonnegative fractions (rational numbers).
         */
        public class Fraction {
    
          /* private fields within a Fraction. */
          private static int numberOfFractions = 0;//change type to static,part 3
    
          private int numerator;
          private int denominator;
    
          /** Constructs a Fraction n/d. 
           *  @param n is the numerator.  Must be nonnegative.
           *  @param d is the denominator.  Must be positive.
           */
          public Fraction(int n, int d) {
            if (n < 0) {
              System.out.println("Fatal error:  Negative numerator.");
              System.exit(0);
            }
            if (d < 1) {
              System.out.println("Fatal error:  Nonpositive denominator.");
              System.exit(0);
            }
            numberOfFractions++;
            numerator = n; 
            denominator = d;
          }
    
          /** Constructs a Fraction n/1. 
           *  @param n is the numerator.  Must be nonnegative.
           */
          public Fraction(int n) {
            this(n, 1);
          }
    
          /** Constructs a Fraction 0/1. 
           */
          public Fraction() {
            this(0,1);//part1 更改过后的constructor
          }
    
          /** Copies the Fraction "original".
           */
          public int getNumerator(){
              return numerator;
          }
          public int getDenominator(){
              return denominator;
          }
          
          public Fraction(Fraction original) {
            this(original.getNumerator(),original.getDenominator());
          }//part2 修改后的constructor
    
          /** Converts this Fraction to a string format:  "numerator/denominator."
           *  Fractions should be printed in reduced form (part of your assignment is
           *  to make this true).
           *  @return a String representation of this Fraction.
           */
          public String toString() {
            int thisGcd = gcd(numerator, denominator);
    
            return (numerator / thisGcd + "/" + denominator / thisGcd);
          }
    
          /** Return the sum of two fractions.
           *  @param f2 is the Fraction to be added.
           *  @return the result of adding f2 to this Fraction.
           */
          public Fraction add(Fraction f2) {
            Fraction r = new Fraction((numerator * f2.denominator) +
                          (f2.numerator * denominator),
                          denominator * f2.denominator);
            return r;
          }
    
          /** Replaces this Fraction's numerator with a new value.
           *  @param numerator is the new numerator.  Must be nonnegative.
           */
          public void changeNumerator(int numerator) { // DO NOT CHANGE THIS SIGNATURE!
            // Fix the bug that prevents this method from working correctly.
            if (numerator < 0) {
              System.out.println("Fatal error:  Negative numerator.");
              System.exit(0);
            }
           this. numerator = numerator;//change numerator to this.numerator,part3
          }
    
          /** Returns the number of Fraction objects in existence.
           *  @return the number of Fraction objects in existence.
           */
          public int fracs() {                         // DO NOT CHANGE THIS SIGNATURE!
            // Fix the bug that prevents this method from working correctly.
            return numberOfFractions;
          }
    
          /** Computes the greatest common divisor (gcd) of the two inputs.
           * @param x must be nonnegative
           * @param y must be nonnegative
           * @return the gcd of x and y
           */
          static private int gcd(int x, int y) {
            /* Replace the following line with your solution. */
            if(y==0)
                return x;
            else
                return gcd(y,x%y);
          }//part 4,the greatest common divisor of numerator and denominator;
    
          /** Put the Fraction class through some tests.
           * @param argv is not used.
           */
          public static void main(String[] argv) {
    
            /* Test all four contructors and toString. */
            Fraction f0 = new Fraction();
            Fraction f1 = new Fraction(3);
            Fraction f2 = new Fraction(12, 20);
            Fraction f3 = new Fraction(f2);
    
            System.out.println("
    Testing constructors and toString():");
            System.out.println("The fraction f0 is " + f0.toString());
            System.out.println("The fraction f1 is " + f1);    // toString is implicit.
            System.out.println("The fraction f2 is " + f2);
            System.out.println("The fraction f3 is " + f3 + ", which should equal f2");
    
            /* Test the add method. */
            System.out.println("
    Testing add:");
    
            
            Fraction sumOfTwo = f1.add(f2);              // Sum of f1 and f2.part2
            Fraction sumOfThree = f0.add(f1).add(f2);             // Sum of f0, f1, and f2.part2
    
            System.out.println("The sum of " + f1 + " and " + f2 + " is " + sumOfTwo);
            System.out.println("The sum of " + f0 + ", " + f1 + " and " + f2 + " is " +
                               sumOfThree);
            
    
            /* Test the methods used in Part III. */
            System.out.println("
    Testing changeNumerator and fracs:");
    
            f3.changeNumerator(7);
            System.out.println("Now f3 is " + f3 + ", which should be 7/20");
            System.out.println("The total number of Fraction objects is " +
                               f3.fracs());
    
            /* Test gcd function (static method). */
            System.out.println("
    Testing gcd:");
            System.out.println("The gcd of 2 and 10 is: " + gcd(2, 10));
            System.out.println("The gcd of 15 and 5 is: " + gcd(15, 5));
            System.out.println("The gcd of 24 and 18 is: " + gcd(24, 18));
            System.out.println("The gcd of 10 and 10 is: " + gcd(10, 10));
            System.out.println("The gcd of 21 and 400 is: " + gcd(21, 400));
          }
        }

    主要复习了constructor的应用,this的应用,以及辗转相除法求最大公约数;

    运行结果:

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  • 原文地址:https://www.cnblogs.com/lyz1995/p/7146827.html
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