CompareUtil.java

package gov.usgs.earthquake.util;

/**
 * Utility class for comparing potentially null values.
 */
public class CompareUtil {

  /**
   * A method to simplify comparison of two values, either of which may be null.
   *
   * For purposes of this comparison, null values are > non-null values.
   *
   * @param a   value to compare
   * @param b   value to compare
   * @param <T> type
   * @return -1, if a is not null and b is null; 0, if a is null and b is null; 1,
   *         if a is null and b is not null; otherwise, a.compareTo(b).
   */
  public static <T extends Comparable<T>> int nullSafeCompare(final T a, final T b) {
    if (a == null && b != null) {
      // null > real values
      return 1;
    } else if (a != null && b == null) {
      // real values < null
      return -1;
    } else if (a == null && b == null) {
      // null == null
      return 0;
    } else {
      // not null, use object compareTo
      return a.compareTo(b);
    }
  }

}