fraction.java

一个很好的微工作流内核

/*
  File: Fraction.java

  Originally written by Doug Lea and released into the public domain.
  This may be used for any purposes whatsoever without acknowledgment.
  Thanks for the assistance and support of Sun Microsystems Labs,
  and everyone contributing, testing, and using this code.

  History:
  Date       Who                What
  7Jul1998  dl               Create public version
  11Oct1999 dl               add hashCode
*/

package EDU.oswego.cs.dl.util.concurrent.misc;


/**
 * An immutable class representing fractions as pairs of longs.
 * Fractions are always maintained in reduced form.
 **/
public class Fraction implements Cloneable, Comparable, java.io.Serializable {
  protected final long numerator_;
  protected final long denominator_;

  /** Return the numerator **/
  public final long numerator() { return numerator_; }

  /** Return the denominator **/
  public final long denominator() { return denominator_; }

  /** Create a Fraction equal in value to num / den **/
  public Fraction(long num, long den) {
    // normalize while constructing
    boolean numNonnegative = (num >= 0);
    boolean denNonnegative = (den >= 0);
    long a = numNonnegative? num : -num;
    long b = denNonnegative? den : -den;
    long g = gcd(a, b);
    numerator_ = (numNonnegative == denNonnegative)? (a / g) : (-a / g);
    denominator_ = b / g;
  }

  /** Create a fraction with the same value as Fraction f **/
  public Fraction(Fraction f) {
    numerator_ = f.numerator();
    denominator_ = f.denominator();
  }

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

  public Object clone() { return new Fraction(this); }

  /** Return the value of the Fraction as a double **/
  public double asDouble() { 
    return ((double)(numerator())) / ((double)(denominator()));
  }

  /** 
   * Compute the nonnegative greatest common divisor of a and b.
   * (This is needed for normalizing Fractions, but can be
   * useful on its own.)
   **/
  public static long gcd(long a, long b) { 
    long x;
    long y;

    if (a < 0) a = -a;
    if (b < 0) b = -b;

    if (a >= b) { x = a; y = b; }
    else        { x = b; y = a; }

    while (y != 0) {
      long t = x % y;
      x = y;
      y = t;
    }
    return x;
  }

  /** return a Fraction representing the negated value of this Fraction **/
  public Fraction negative() {
    long an = numerator();
    long ad = denominator();
    return new Fraction(-an, ad);
  }

  /** return a Fraction representing 1 / this Fraction **/
  public Fraction inverse() {
    long an = numerator();
    long ad = denominator();
    return new Fraction(ad, an);
  }


  /** return a Fraction representing this Fraction plus b **/
  public Fraction plus(Fraction b) {
    long an = numerator();
    long ad = denominator();
    long bn = b.numerator();
    long bd = b.denominator();
    return new Fraction(an*bd+bn*ad, ad*bd);
  }

  /** return a Fraction representing this Fraction plus n **/
  public Fraction plus(long n) {
    long an = numerator();
    long ad = denominator();
    long bn = n;
    long bd = 1;
    return new Fraction(an*bd+bn*ad, ad*bd);
  }

  /** return a Fraction representing this Fraction minus b **/
  public Fraction minus(Fraction b) {
    long an = numerator();
    long ad = denominator();
    long bn = b.numerator();
    long bd = b.denominator();
    return new Fraction(an*bd-bn*ad, ad*bd);
  }

  /** return a Fraction representing this Fraction minus n **/
  public Fraction minus(long n) {
    long an = numerator();
    long ad = denominator();
    long bn = n;
    long bd = 1;
    return new Fraction(an*bd-bn*ad, ad*bd);
  }


  /** return a Fraction representing this Fraction times b **/
  public Fraction times(Fraction b) {
    long an = numerator();
    long ad = denominator();
    long bn = b.numerator();
    long bd = b.denominator();
    return new Fraction(an*bn, ad*bd);
  }

  /** return a Fraction representing this Fraction times n **/
  public Fraction times(long n) {
    long an = numerator();
    long ad = denominator();
    long bn = n;
    long bd = 1;
    return new Fraction(an*bn, ad*bd);
  }

  /** return a Fraction representing this Fraction divided by b **/
  public Fraction dividedBy(Fraction b) {
    long an = numerator();
    long ad = denominator();
    long bn = b.numerator();
    long bd = b.denominator();
    return new Fraction(an*bd, ad*bn);
  }

  /** return a Fraction representing this Fraction divided by n **/
  public Fraction dividedBy(long n) {
    long an = numerator();
    long ad = denominator();
    long bn = n;
    long bd = 1;
    return new Fraction(an*bd, ad*bn);
  }

  /** return a number less, equal, or greater than zero
   * reflecting whether this Fraction is less, equal or greater than 
   * the value of Fraction other.
   **/
  public int compareTo(Object other) {
    Fraction b = (Fraction)(other);
    long an = numerator();
    long ad = denominator();
    long bn = b.numerator();
    long bd = b.denominator();
    long l = an*bd;
    long r = bn*ad;
    return (l < r)? -1 : ((l == r)? 0: 1);
  }

  /** return a number less, equal, or greater than zero
   * reflecting whether this Fraction is less, equal or greater than n.
   **/

  public int compareTo(long n) {
    long an = numerator();
    long ad = denominator();
    long bn = n;
    long bd = 1;
    long l = an*bd;
    long r = bn*ad;
    return (l < r)? -1 : ((l == r)? 0: 1);
  }

  public boolean equals(Object other) {
    return compareTo((Fraction)other) == 0;
  }

  public boolean equals(long n) {
    return compareTo(n) == 0;
  }

  public int hashCode() {
    return (int) (numerator_ ^ denominator_);
  }

}