rational.java

java程序设计导论（daniel liang著） 所有偶数课后习题答案

// Rational.java: Define a rational number and its associated
// operations such as add, subtract, multiply, and divide
public class Rational extends Number implements Comparable {
  // Data fields for numerator and denominator
  private long numerator = 0;
  private long denominator = 1;

  /** Default constructor */
  public Rational() {
    this(0, 1);
  }

  /** Construct a rational with specified numerator and denominator */
  public Rational(long numerator, long denominator) {
    long gcd = gcd(numerator, denominator);
    this.numerator = ((denominator > 0) ? 1 : -1) * numerator / gcd;
    this.denominator = Math.abs(denominator) / gcd;
  }

  /** Find GCD of two numbers */
  private long gcd(long n, long d) {
    long t1 = Math.abs(n);
    long t2 = Math.abs(d);
    long remainder = t1 % t2;

    while (remainder != 0) {
      t1 = t2;
      t2 = remainder;
      remainder = t1%t2;
    }

    return t2;
  }

  /** Return numerator */
  public long getNumerator() {
    return numerator;
  }

  /** Return denominator */
  public long getDenominator() {
    return denominator;
  }

  /** Add a rational number to this rational */
  public Rational add(Rational secondRational) {
    long n = numerator * secondRational.getDenominator() +
      denominator * secondRational.getNumerator();
    long d = denominator * secondRational.getDenominator();
    return new Rational(n, d);
  }

  /** Subtract a rational number from this rational */
  public Rational subtract(Rational secondRational) {
    long n = numerator * secondRational.getDenominator()
      - denominator * secondRational.getNumerator();
    long d = denominator * secondRational.getDenominator();
    return new Rational(n, d);
  }

  /** Multiply a rational number to this rational */
  public Rational multiply(Rational secondRational) {
    long n = numerator * secondRational.getNumerator();
    long d = denominator * secondRational.getDenominator();
    return new Rational(n, d);
  }

  /** Divide a rational number from this rational */
  public Rational divide(Rational secondRational) {
    long n = numerator * secondRational.getDenominator();
    long d = denominator * secondRational.numerator;
    return new Rational(n, d);
  }

  /** Override the toString() method */
  public String toString() {
    if (denominator == 1)
      return numerator + "";
    else
      return numerator + "/" + denominator;
  }

  /** Override the equals method in the Object class */
  public boolean equals(Object parm1) {
    if ((this.subtract((Rational)(parm1))).getNumerator() == 0)
      return true;
    else
      return false;
  }

  /** Override the hashCode method in the Object class */
  public int hashCode() {
    return new Double(this.doubleValue()).hashCode();
  }

  /** Override the abstract intValue method in java.lang.Number */
  public int intValue() {
    return (int)doubleValue();
  }

  /** Override the abstract floatValue method in java.lang.Number */
  public float floatValue() {
    return (float)doubleValue();
  }

  /** Override the doubleValue method in java.lang.Number */
  public double doubleValue() {
    return numerator * 1.0 / denominator;
  }

  /** Override the abstract longValue method in java.lang.Number */
  public long longValue() {
    return (long)doubleValue();
  }

  /** Override the compareTo method in java.lang.Comparable */
  public int compareTo(Object o) {
    if ((this.subtract((Rational)o)).getNumerator() > 0)
      return 1;
    else if ((this.subtract((Rational)o)).getNumerator() < 0)
      return -1;
    else
      return 0;
  }
}