Format a Map : Map « Collections Data Structure « Java

Format a Map


 * Created on Jan 25, 2008
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 * Copyright @2008 the original author or authors.
//package org.fest.util;

import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;

 * Understands utility methods related to maps.
 * @author Yvonne Wang
 * @author Alex Ruiz
public class Maps {

   * Returns <code>true</code> if the given map is <code>null</code> or empty.
   * @param map the map to check.
   * @return <code>true</code> if the given map is <code>null</code> or empty, otherwise <code>false</code>.
  public static boolean isEmpty(Map<?, ?> map) {
    return map == null || map.isEmpty();

   * Returns the <code>String</code> representation of the given map, or <code>null</code> if the given map is
   * <code>null</code>.
   * @param map the map to format.
   * @return the <code>String</code> representation of the given map.
  public static String format(Map<?, ?> map) {
    if (map == null) return null;
    Iterator<?> i = map.entrySet().iterator();
    if (!i.hasNext()) return "{}";
    StringBuilder b = new StringBuilder();
    for (;;) {
      Entry<?, ?> e = (Entry<?, ?>);
      b.append(format(map, e.getKey()));
      b.append(format(map, e.getValue()));
      if (!i.hasNext()) return b.append("}").toString();
      b.append(", ");

  private static Object format(Map<?, ?> map, Object o) {
    return o == map ? "(this Map)" : "\" "+ o+"\" ";

  private Maps() {}


Related examples in the same category

1.Creating and storing arrays in a map
2.Sort based on the values
3.Get a key from value with an HashMap
4.Retrieve environment variables (JDK1.5)
5.Creating a Type-Specific Map: creates a map whose keys are Integer objects and values are String objects.
6.A map declared to hold objects of a type T can also hold objects that extend from T
7.A value retrieved from a type-specific collection does not need to be casted
8.Map techniques.
9.Create an array containing the keys in a map
10.Create an array containing the values in a map
11.Creating a Hash Table
12.Creating a Map That Retains Order-of-Insertion
13.Automatically Removing an Unreferenced Element from a Hash Table
14.Creating a Type-Specific Map [5.0]
15.Use Iterator to loop through the HashMap class
16.Create type specific collections
17.Convert Properties into Map
18.A java.util.Map implementation using reference values
19.Utility method that return a String representation of a map. The elements will be represented as "key = value"
20.Utility method that return a String representation of a map. The elements will be represented as "key = value" (tab)
21.This program demonstrates the use of a map with key type String and value type Employee
22.A Map implementation that dumps its content when memory runs low.
23.A Map that stores the values in files within a directory.
24.Map List
25.Multi Value Map Array List
26.Multi Value Map Linked HashSet
27.An object that maps keys to values, and values back to keys.
28.LRU Map
29.A map acts like array.
30.Order Retaining Map
31.BinaryMap class implements a map from objects to integer objects where the only value is the integer with value 1.
32.A space-optimized map for associating char keys with values.
33.A Map implementation that grows to a fixed size and then retains only a fixed number of the highest (largest) keys.
34.Class which creates mapping between keys and a list of values.
35.A map of values by class.
36.History Map
37.Sorts map by values in ascending order.
38.Map from a given key to a list of values
39.Map from a given key to a set of values
40.Class which keeps a set of values and assigns each value a unique positive index.
41.Array Map
42.Array map
43.An ArrayMap is a very inefficient map type that is more robust in dealing with changes to its keys than other maps.
44.This Map stores it's keys as strings in upper case, null and duplicate keys are not allowed
45.Map to string
46.A simple class that stores key Strings as char[]'s in a hash table.