java/src/main/com/google/appengine/api/search/Util.java

   1 // Copyright 2010 Google Inc. All Rights Reserved.
   2
   3 package com.google.appengine.api.search;
   4
   5 import java.util.Date;
   6 import java.util.Iterator;
   7 import java.util.LinkedList;
   8
   9 /**
  10  * A utility class that does various checks on search and indexing parameters.
  11  *
  12  */
  13 public final class Util {
  14
  15   private static final long MILLISECONDS_IN_DAY = 1000L * 60 * 60 * 24;
  16
  17   private Util() {
  18   }
  19
  20   /**
  21    * @return whether or not the string is null or empty
  22    */
  23   public static boolean isNullOrEmpty(String string) {
  24     return string == null || string.isEmpty();
  25   }
  26
  27   /**
  28    * A helper method for testing two objects are equal.
  29    *
  30    * @return whether the two objects a and b are equal
  31    */
  32   public static boolean equalObjects(Object a, Object b) {
  33     return a == b || (a != null && a.equals(b));
  34   }
  35
  36   /**
  37    * A helper method for overriding null values with a default value.
  38    *
  39    * @param value the value of some field
  40    * @param defaultValue the default value for the field
  41    * @return value if it is not null, otherwise the defaultValue
  42    */
  43   public static <T> T defaultIfNull(T value, T defaultValue) {
  44     return value == null ? defaultValue : value;
  45   }
  46
  47   /**
  48    * Returns a string representation of the iterable objects. This is
  49    * used in debugging. The limit parameter is used to control how many
  50    * elements of the iterable are used to build the final string. Use
  51    * 0 or negative values, to include all.
  52    *
  53    * @param objects an iterable of objects to be turned into a string
  54    * @param limit the maximum number of objects from iterable to be used
  55    * to build a string
  56    */
  57   public static <T> String iterableToString(Iterable<T> objects, int limit) {
  58     StringBuilder builder = new StringBuilder()
  59         .append("[");
  60     String sep = "";
  61     int head = (limit <= 0) ? Integer.MAX_VALUE : (limit + 1) / 2;
  62     int tail = (limit <= 0) ? 0 : limit - head;
  63     Iterator<T> iter = objects.iterator();
  64     while (iter.hasNext() && --head >= 0) {
  65       builder.append(sep).append(iter.next().toString());
  66       sep = ", ";
  67     }
  68     LinkedList<T> tailMembers = new LinkedList<T>();
  69     int seen = 0;
  70     while (iter.hasNext()) {
  71       tailMembers.add(iter.next());
  72       if (++seen > tail) {
  73         tailMembers.removeFirst();
  74       }
  75     }
  76     if (seen > tail) {
  77       builder.append(", ...");
  78     }
  79     for (T o : tailMembers) {
  80       builder.append(sep).append(o.toString());
  81       sep = ", ";
  82     }
  83     return builder.append("]").toString();
  84   }
  85
  86   /**
  87    * Returns a string which can be used to append an iterable field to a debug
  88    * string.
  89    */
  90   public static <T> String iterableFieldToString(String fieldName, Iterable<T> objects) {
  91     if (!objects.iterator().hasNext()) {
  92       return "";
  93     }
  94     return String.format(", %s=%s", fieldName, Util.iterableToString(objects, 0));
  95   }
  96
  97   /**
  98    * Returns a string that allows a field value pair to be added to a debug
  99    * string.
 100    */
 101   public static String fieldToString(String name, Object value) {
 102     return fieldToString(name, value, false);
 103   }
 104
 105   /**
 106    * Returns a string that allows a field value pair to be added to a debug
 107    * string.
 108    */
 109   public static String fieldToString(String name, Object value, boolean firstParameter) {
 110     if (value == null) {
 111       return "";
 112     }
 113     if (firstParameter) {
 114       return String.format("%s=%s",  name, value);
 115     }
 116     return String.format(", %s=%s",  name, value);
 117   }
 118
 119   /**
 120    * Converts a given date to a numeric value, ignoring any time component.
 121    *
 122    * @param date the date to convert to an int
 123    * @return a number representing the given date
 124    * @deprecated as of 1.7.2
 125    */
 126   @Deprecated
 127   public static int getIntForDate(Date date) {
 128     return (int) (date.getTime() / MILLISECONDS_IN_DAY);
 129   }
 130 }