CompareUtil.java

  1. package gov.usgs.earthquake.util;

  3. /**
  4.  * Utility class for comparing potentially null values.
  5.  */
  6. public class CompareUtil {

  8.     /**
  9.      * A method to simplify comparison of two values, either of which may be
  10.      * null.
  11.      *
  12.      * For purposes of this comparison, null values are > non-null values.
  13.      *
  14.      * @param a
  15.      *            value to compare
  16.      * @param b
  17.      *            value to compare
  18.      * @param <T>
  19.      *            type
  20.      * @return -1, if a is not null and b is null; 0, if a is null and b is
  21.      *         null; 1, if a is null and b is not null; otherwise,
  22.      *         a.compareTo(b).
  23.      */
  24.     public static <T extends Comparable<T>> int nullSafeCompare(final T a, final T b) {
  25.         if (a == null && b != null) {
  26.             // null > real values
  27.             return 1;
  28.         } else if (a != null && b == null) {
  29.             // real values < null
  30.             return -1;
  31.         } else if (a == null && b == null) {
  32.             // null == null
  33.             return 0;
  34.         } else {
  35.             // not null, use object compareTo
  36.             return a.compareTo(b);
  37.         }
  38.     }

  40. }
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