maputils.java

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            out.println("null");
            return;
        }
        if (label != null) {
            out.print(label);
            out.println(" = ");
        }

        printIndent(out, lineage.size());
        out.println("{");

        lineage.push(map);

        for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
            Map.Entry entry = (Map.Entry) it.next();
            Object childKey = entry.getKey();
            Object childValue = entry.getValue();
            if (childValue instanceof Map && !lineage.contains(childValue)) {
                verbosePrintInternal(
                    out,
                    (childKey == null ? "null" : childKey),
                    (Map) childValue,
                    lineage,
                    debug);
            } else {
                printIndent(out, lineage.size());
                out.print(childKey);
                out.print(" = ");
                
                final int lineageIndex = lineage.indexOf(childValue);
                if (lineageIndex == -1) {
                    out.print(childValue);
                } else if (lineage.size() - 1 == lineageIndex) {
                    out.print("(this Map)");    
                } else {
                    out.print(
                        "(ancestor["
                            + (lineage.size() - 1 - lineageIndex - 1)
                            + "] Map)");
                }
                
                if (debug && childValue != null) {
                    out.print(' ');
                    out.println(childValue.getClass().getName());
                } else {
                    out.println();
                }
            }
        }
        
        lineage.pop();

        printIndent(out, lineage.size());
        out.println(debug ? "} " + map.getClass().getName() : "}");
    }

    /**
     * Writes indentation to the given stream.
     *
     * @param out  the stream to indent
     */
    private static void printIndent(final PrintStream out, final int indent) {
        for (int i = 0; i < indent; i++) {
            out.print(INDENT_STRING);
        }
    }
    
    // Misc
    //-----------------------------------------------------------------------
    /**
     * Inverts the supplied map returning a new HashMap such that the keys of
     * the input are swapped with the values.
     * <p>
     * This operation assumes that the inverse mapping is well defined.
     * If the input map had multiple entries with the same value mapped to
     * different keys, the returned map will map one of those keys to the 
     * value, but the exact key which will be mapped is undefined.
     *
     * @param map  the map to invert, may not be null
     * @return a new HashMap containing the inverted data
     * @throws NullPointerException if the map is null
     */
    public static Map invertMap(Map map) {
        Map out = new HashMap(map.size());
        for (Iterator it = map.entrySet().iterator(); it.hasNext();) {
            Map.Entry entry = (Map.Entry) it.next();
            out.put(entry.getValue(), entry.getKey());
        }
        return out;
    }
     
    //-----------------------------------------------------------------------
    /**
     * Protects against adding null values to a map.
     * <p>
     * This method checks the value being added to the map, and if it is null
     * it is replaced by an empty string.
     * <p>
     * This could be useful if the map does not accept null values, or for
     * receiving data from a source that may provide null or empty string
     * which should be held in the same way in the map.
     * <p>
     * Keys are not validated.
     * 
     * @param map  the map to add to, may not be null
     * @param key  the key
     * @param value  the value, null converted to ""
     * @throws NullPointerException if the map is null
     */
    public static void safeAddToMap(Map map, Object key, Object value) throws NullPointerException {
        if (value == null) {
            map.put(key, "");
        } else {
            map.put(key, value);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Puts all the keys and values from the specified array into the map.
     * <p>
     * This method is an alternative to the {@link java.util.Map#putAll(java.util.Map)}
     * method and constructors. It allows you to build a map from an object array
     * of various possible styles.
     * <p>
     * If the first entry in the object array implements {@link java.util.Map.Entry}
     * or {@link KeyValue} then the key and value are added from that object.
     * If the first entry in the object array is an object array itself, then
     * it is assumed that index 0 in the sub-array is the key and index 1 is the value.
     * Otherwise, the array is treated as keys and values in alternate indices.
     * <p>
     * For example, to create a color map:
     * <pre>
     * Map colorMap = MapUtils.putAll(new HashMap(), new String[][] {
     *     {"RED", "#FF0000"},
     *     {"GREEN", "#00FF00"},
     *     {"BLUE", "#0000FF"}
     * });
     * </pre>
     * or:
     * <pre>
     * Map colorMap = MapUtils.putAll(new HashMap(), new String[] {
     *     "RED", "#FF0000",
     *     "GREEN", "#00FF00",
     *     "BLUE", "#0000FF"
     * });
     * </pre>
     * or:
     * <pre>
     * Map colorMap = MapUtils.putAll(new HashMap(), new Map.Entry[] {
     *     new DefaultMapEntry("RED", "#FF0000"),
     *     new DefaultMapEntry("GREEN", "#00FF00"),
     *     new DefaultMapEntry("BLUE", "#0000FF")
     * });
     * </pre>
     *
     * @param map  the map to populate, must not be null
     * @param array  an array to populate from, null ignored
     * @return the input map
     * @throws NullPointerException  if map is null
     * @throws IllegalArgumentException  if sub-array or entry matching used and an
     *  entry is invalid
     * @throws ClassCastException if the array contents is mixed
     * @since Commons Collections 3.2
     */
    public static Map putAll(Map map, Object[] array) {
        map.size();  // force NPE
        if (array == null || array.length == 0) {
            return map;
        }
        Object obj = array[0];
        if (obj instanceof Map.Entry) {
            for (int i = 0; i < array.length; i++) {
                Map.Entry entry = (Map.Entry) array[i];
                map.put(entry.getKey(), entry.getValue());
            }
        } else if (obj instanceof KeyValue) {
            for (int i = 0; i < array.length; i++) {
                KeyValue keyval = (KeyValue) array[i];
                map.put(keyval.getKey(), keyval.getValue());
            }
        } else if (obj instanceof Object[]) {
            for (int i = 0; i < array.length; i++) {
                Object[] sub = (Object[]) array[i];
                if (sub == null || sub.length < 2) {
                    throw new IllegalArgumentException("Invalid array element: " + i);
                }
                map.put(sub[0], sub[1]);
            }
        } else {
            for (int i = 0; i < array.length - 1;) {
                map.put(array[i++], array[i++]);
            }
        }
        return map;
    }

    //-----------------------------------------------------------------------
    /**
     * Null-safe check if the specified map is empty.
     * <p>
     * Null returns true.
     * 
     * @param map  the map to check, may be null
     * @return true if empty or null
     * @since Commons Collections 3.2
     */
    public static boolean isEmpty(Map map) {
        return (map == null || map.isEmpty());
    }

    /**
     * Null-safe check if the specified map is not empty.
     * <p>
     * Null returns false.
     * 
     * @param map  the map to check, may be null
     * @return true if non-null and non-empty
     * @since Commons Collections 3.2
     */
    public static boolean isNotEmpty(Map map) {
        return !MapUtils.isEmpty(map);
    }

    // Map decorators
    //-----------------------------------------------------------------------
    /**
     * Returns a synchronized map backed by the given map.
     * <p>
     * You must manually synchronize on the returned buffer's iterator to 
     * avoid non-deterministic behavior:
     *  
     * <pre>
     * Map m = MapUtils.synchronizedMap(myMap);
     * Set s = m.keySet();  // outside synchronized block
     * synchronized (m) {  // synchronized on MAP!
     *     Iterator i = s.iterator();
     *     while (i.hasNext()) {
     *         process (i.next());
     *     }
     * }
     * </pre>
     * 
     * This method uses the implementation in {@link java.util.Collections Collections}.
     * 
     * @param map  the map to synchronize, must not be null
     * @return a synchronized map backed by the given map
     * @throws IllegalArgumentException  if the map is null
     */
    public static Map synchronizedMap(Map map) {
        return Collections.synchronizedMap(map);
    }

    /**
     * Returns an unmodifiable map backed by the given map.
     * <p>
     * This method uses the implementation in the decorators subpackage.
     *
     * @param map  the map to make unmodifiable, must not be null
     * @return an unmodifiable map backed by the given map
     * @throws IllegalArgumentException  if the map is null
     */
    public static Map unmodifiableMap(Map map) {
        return UnmodifiableMap.decorate(map);
    }

    /**
     * Returns a predicated (validating) map backed by the given map.
     * <p>
     * Only objects that pass the tests in the given predicates can be added to the map.
     * Trying to add an invalid object results in an IllegalArgumentException.
     * Keys must pass the key predicate, values must pass the value predicate.
     * It is important not to use the original map after invoking this method,
     * as it is a backdoor for adding invalid objects.
     *
     * @param map  the map to predicate, must not be null
     * @param keyPred  the predicate for keys, null means no check
     * @param valuePred  the predicate for values, null means no check
     * @return a predicated map backed by the given map
     * @throws IllegalArgumentException  if the Map is null
     */
    public static Map predicatedMap(Map map, Predicate keyPred, Predicate valuePred) {
        return PredicatedMap.decorate(map, keyPred, valuePred);
    }

    /**
     * Returns a typed map backed by the given map.
     * <p>
     * Only keys and values of the specified types can be added to the map.
     * 
     * @param map  the map to limit to a specific type, must not be null
     * @param keyType  the type of keys which may be added to the map, must not be null
     * @param valueType  the type of values which may be added to the map, must not be null
     * @return a typed map backed by the specified map
     * @throws IllegalArgumentException  if the Map or Class is null
     */
    public static Map typedMap(Map map, Class keyType, Class valueType) {
        return TypedMap.decorate(map, keyType, valueType);
    }
    
    /**
     * Returns a transformed map backed by the given map.
     * <p>
     * This method returns a new map (decorating the specified map) that
     * will transform any new entries added to it.
     * Existing entries in the specified map will not be transformed.
     * If you want that behaviour, see {@link TransformedMap#decorateTransform}.
     * <p>
     * Each object is passed through the transformers as it is added to the
     * Map. It is important not to use the original map after invoking this 
     * method, as it is a backdoor for adding untransformed objects.
     * <p>
     * If there are any elements already in the map being decorated, they
     * are NOT transformed.
     *
     * @param map  the map to transform, must not be null, typically empty
     * @param keyTransformer  the transformer for the map keys, null means no transformation
     * @param valueTransformer  the transformer for the map values, null means no transformation
     * @return a transformed map backed by the given map
     * @throws IllegalArgumentException  if the Map is null
     */
    public static Map transformedMap(Map map, Transformer keyTransformer, Transformer valueTransformer) {
        return TransformedMap.decorate(map, keyTransformer, valueTransformer);
    }
    
    /**
     * Returns a fixed-sized map backed by the given map.
     * Elements may not be added or removed from the returned map, but 
     * existing elements can be changed (for instance, via the 
     * {@link Map#put(Object,Object)} method).