Overview  Package   Class  Index 
 PREV CLASS   NEXT CLASS FRAMES    NO FRAMES
SUMMARY:  INNER | FIELD | CONSTR | METHOD DETAIL:  FIELD | CONSTR | METHOD

org.apache.commons.collections
Class MapUtils

java.lang.Object
  |
  +--org.apache.commons.collections.MapUtils
public class MapUtils
extends Object

A helper class for using Map instances.

It contains various typesafe methods as well as other useful features like deep copying.

It also provides the following decorators:

Since:
1.0
Author:
James Strachan, Nissim Karpenstein, Kasper Nielsen, Paul Jack, Stephen Colebourne

Constructor Summary
MapUtils()
          Please don't instantiate a MapUtils.
 
Method Summary
static void debugPrint(PrintStream out, Object key, Map map)
          Prints the given map with nice line breaks.
protected static void debugPrintIndent(PrintStream out)
          Writes indentation to the given stream.
static Map fixedSizeMap(Map map)
          Returns a fixed-sized map backed by the given map.
static SortedMap fixedSizeSortedMap(SortedMap map)
          Returns a fixed-sized sorted map backed by the given sorted map.
static Boolean getBoolean(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Boolean.
static Boolean getBoolean(Map map, Object key, Boolean defaultValue)
          Looks up the given key in the given map, converting the result into a boolean, using the default value if the the conversion fails.
static Byte getByte(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Byte.
static Byte getByte(Map map, Object key, Byte defaultValue)
          Looks up the given key in the given map, converting the result into a byte, using the default value if the the conversion fails.
static Double getDouble(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Double.
static Double getDouble(Map map, Object key, Double defaultValue)
          Looks up the given key in the given map, converting the result into a double, using the default value if the the conversion fails.
static Float getFloat(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Float.
static Float getFloat(Map map, Object key, Float defaultValue)
          Looks up the given key in the given map, converting the result into a float, using the default value if the the conversion fails.
static Integer getInteger(Map map, Object key)
          Looks up the given key in the given map, converting the result into an Integer.
static Integer getInteger(Map map, Object key, Integer defaultValue)
          Looks up the given key in the given map, converting the result into an integer, using the default value if the the conversion fails.
static Long getLong(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Long.
static Long getLong(Map map, Object key, Long defaultValue)
          Looks up the given key in the given map, converting the result into a long, using the default value if the the conversion fails.
static Map getMap(Map map, Object key)
          Looks up the given key in the given map, returning another map.
static Map getMap(Map map, Object key, Map defaultValue)
          Looks up the given key in the given map, converting the result into a map, using the default value if the the conversion fails.
static Number getNumber(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Number.
static Number getNumber(Map map, Object key, Number defaultValue)
          Looks up the given key in the given map, converting the result into a number, using the default value if the the conversion fails.
static Object getObject(Map map, Object key)
          Synonym for Map.get(Object).
static Object getObject(Map map, Object key, Object defaultValue)
          Looks up the given key in the given map, converting null into the given default value.
static Short getShort(Map map, Object key)
          Looks up the given key in the given map, converting the result into a Short.
static Short getShort(Map map, Object key, Short defaultValue)
          Looks up the given key in the given map, converting the result into a short, using the default value if the the conversion fails.
static String getString(Map map, Object key)
          Looks up the given key in the given map, converting the result into a string.
static String getString(Map map, Object key, String defaultValue)
          Looks up the given key in the given map, converting the result into a string, using the default value if the the conversion fails.
static Map lazyMap(Map map, Factory factory)
          Returns a "lazy" map whose values will be created on demand.
static SortedMap lazySortedMap(SortedMap map, Factory factory)
          Returns a "lazy" sorted map whose values will be created on demand.
protected static void logInfo(Exception e)
          Logs the given exception to System.out.
static Map predicatedMap(Map map, Predicate keyPred, Predicate valuePred)
          Returns a predicated map backed by the given map.
static SortedMap predicatedSortedMap(SortedMap map, Predicate keyPred, Predicate valuePred)
          Returns a predicated sorted map backed by the given map.
static void safeAddToMap(Map map, Object key, Object value)
          Nice method for adding data to a map in such a way as to not get NPE's.
static Properties toProperties(Map map)
          Gets a new Properties object initialised with the values from a Map.
static void verbosePrint(PrintStream out, Object key, Map map)
          Prints the given map with nice line breaks.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

MapUtils

public MapUtils()
Please don't instantiate a MapUtils.
Method Detail

getObject

public static Object getObject(Map map,
                               Object key)
Synonym for Map.get(Object).
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
null if the map is null; or the result of map.get(key)

getString

public static String getString(Map map,
                               Object key)
Looks up the given key in the given map, converting the result into a string.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
null if the map is null; null if the value mapped by that key is null; or the toString() result of the value for that key

getBoolean

public static Boolean getBoolean(Map map,
                                 Object key)
Looks up the given key in the given map, converting the result into a Boolean. If the map is null, this method returns null. If the value mapped by the given key is a Boolean, then it is returned as-is. Otherwise, if the value is a string, then if that string ignoring case equals "true", then a true Boolean is returned. Any other string value will result in a false Boolean being returned. OR, if the value is a Number, and that Number is 0, then a false Boolean is returned. Any other Number value results in a true Boolean being returned.

Any value that is not a Boolean, String or Number results in null being returned.

Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Boolean or null

getNumber

public static Number getNumber(Map map,
                               Object key)
Looks up the given key in the given map, converting the result into a Number. If the map is null, this method returns null. Otherwise, if the key maps to a Number, then that number is returned as-is. Otherwise, if the key maps to a String, that string is parsed into a number using the system default NumberFormat.

If the value is not a Number or a String, or if the value is a String that cannot be parsed into a Number, then null is returned.

Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Number or null

getByte

public static Byte getByte(Map map,
                           Object key)
Looks up the given key in the given map, converting the result into a Byte. First, getNumber(Map,Object) is invoked. If the result is null, then null is returned. Otherwise, the byte value of the resulting Number is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Byte or null

getShort

public static Short getShort(Map map,
                             Object key)
Looks up the given key in the given map, converting the result into a Short. First, getNumber(Map,Object) is invoked. If the result is null, then null is returned. Otherwise, the short value of the resulting Number is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Short or null

getInteger

public static Integer getInteger(Map map,
                                 Object key)
Looks up the given key in the given map, converting the result into an Integer. First, getNumber(Map,Object) is invoked. If the result is null, then null is returned. Otherwise, the integer value of the resulting Number is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
an Integer or null

getLong

public static Long getLong(Map map,
                           Object key)
Looks up the given key in the given map, converting the result into a Long. First, getNumber(Map,Object) is invoked. If the result is null, then null is returned. Otherwise, the long value of the resulting Number is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Long or null

getFloat

public static Float getFloat(Map map,
                             Object key)
Looks up the given key in the given map, converting the result into a Float. First, getNumber(Map,Object) is invoked. If the result is null, then null is returned. Otherwise, the float value of the resulting Number is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Float or null

getDouble

public static Double getDouble(Map map,
                               Object key)
Looks up the given key in the given map, converting the result into a Double. First, getNumber(Map,Object) is invoked. If the result is null, then null is returned. Otherwise, the double value of the resulting Number is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Double or null

getMap

public static Map getMap(Map map,
                         Object key)
Looks up the given key in the given map, returning another map. If the given map is null or if the given key doesn't map to another map, then this method returns null. Otherwise the mapped map is returned.
Parameters:
map - the map whose value to look up
key - the key whose value to look up in that map
Returns:
a Map or null

getObject

public static Object getObject(Map map,
                               Object key,
                               Object defaultValue)
Looks up the given key in the given map, converting null into the given default value.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null
Returns:
the value in the map, or defaultValue if the original value is null or the map is null

getString

public static String getString(Map map,
                               Object key,
                               String defaultValue)
Looks up the given key in the given map, converting the result into a string, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a string, or defaultValue if the original value is null, the map is null or the string conversion fails

getBoolean

public static Boolean getBoolean(Map map,
                                 Object key,
                                 Boolean defaultValue)
Looks up the given key in the given map, converting the result into a boolean, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a boolean, or defaultValue if the original value is null, the map is null or the boolean conversion fails

getNumber

public static Number getNumber(Map map,
                               Object key,
                               Number defaultValue)
Looks up the given key in the given map, converting the result into a number, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getByte

public static Byte getByte(Map map,
                           Object key,
                           Byte defaultValue)
Looks up the given key in the given map, converting the result into a byte, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getShort

public static Short getShort(Map map,
                             Object key,
                             Short defaultValue)
Looks up the given key in the given map, converting the result into a short, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getInteger

public static Integer getInteger(Map map,
                                 Object key,
                                 Integer defaultValue)
Looks up the given key in the given map, converting the result into an integer, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getLong

public static Long getLong(Map map,
                           Object key,
                           Long defaultValue)
Looks up the given key in the given map, converting the result into a long, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getFloat

public static Float getFloat(Map map,
                             Object key,
                             Float defaultValue)
Looks up the given key in the given map, converting the result into a float, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getDouble

public static Double getDouble(Map map,
                               Object key,
                               Double defaultValue)
Looks up the given key in the given map, converting the result into a double, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the number conversion fails

getMap

public static Map getMap(Map map,
                         Object key,
                         Map defaultValue)
Looks up the given key in the given map, converting the result into a map, using the default value if the the conversion fails.
Parameters:
map - the map whose value to look up
key - the key of the value to look up in that map
defaultValue - what to return if the value is null or if the conversion fails
Returns:
the value in the map as a number, or defaultValue if the original value is null, the map is null or the map conversion fails

toProperties

public static Properties toProperties(Map map)
Gets a new Properties object initialised with the values from a Map. A null input will return an empty properties object.
Parameters:
map - the map to convert to a Properties object
Returns:
the properties object

verbosePrint

public static void verbosePrint(PrintStream out,
                                Object key,
                                Map map)
Prints the given map with nice line breaks.
Parameters:
out - the stream to print to
key - the key that maps to the map in some other map
map - the map to print

debugPrint

public static void debugPrint(PrintStream out,
                              Object key,
                              Map map)
Prints the given map with nice line breaks.
Parameters:
out - the stream to print to
key - the key that maps to the map in some other map
map - the map to print

debugPrintIndent

protected static void debugPrintIndent(PrintStream out)
Writes indentation to the given stream.
Parameters:
out - the stream to indent

logInfo

protected static void logInfo(Exception e)
Logs the given exception to System.out.
Parameters:
e - the exception to log

safeAddToMap

public static final void safeAddToMap(Map map,
                                      Object key,
                                      Object value)
                               throws NullPointerException
Nice method for adding data to a map in such a way as to not get NPE's. The point being that if the value is null, map.put() will throw an exception. That blows in the case of this class cause you may want to essentially treat put("Not Null", null ) == put("Not Null", "") We will still throw a NPE if the key is null cause that should never happen.

predicatedMap

public static Map predicatedMap(Map map,
                                Predicate keyPred,
                                Predicate valuePred)
Returns a predicated map backed by the given map. Only keys and values that pass the given predicates can be added to the map. It is important not to use the original map after invoking this method, as it is a backdoor for adding unvalidated objects.
Parameters:
map - the map to predicate, must not be null
keyPred - the predicate for keys, must not be null
valuePred - the predicate for values, must not be null
Returns:
a predicated map backed by the given map
Throws:
IllegalArgumentException - if the Map or Predicates are null

fixedSizeMap

public static Map fixedSizeMap(Map map)
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 Map.put(Object,Object) method).
Parameters:
map - the map whose size to fix, must not be null
Returns:
a fixed-size map backed by that map
Throws:
IllegalArgumentException - if the Map is null

lazyMap

public static Map lazyMap(Map map,
                          Factory factory)
Returns a "lazy" map whose values will be created on demand.

When the key passed to the returned map's Map.get(Object) method is not present in the map, then the factory will be used to create a new object and that object will become the value associated with that key.

For instance: 

 Factory factory = new Factory() {
     public Object create() {
         return new Date();
     }
 }
 Map lazy = MapUtils.lazyMap(new HashMap(), factory);
 Object obj = lazy.get("test");
After the above code is executed, obj will contain a new Date instance. Furthermore, that Date instance is the value for the test key.
Parameters:
map - the map to make lazy, must not be null
factory - the factory for creating new objects, must not be null
Returns:
a lazy map backed by the given map
Throws:
IllegalArgumentException - if the Map or Factory is null

predicatedSortedMap

public static SortedMap predicatedSortedMap(SortedMap map,
                                            Predicate keyPred,
                                            Predicate valuePred)
Returns a predicated sorted map backed by the given map. Only keys and values that pass the given predicates can be added to the map. It is important not to use the original map after invoking this method, as it is a backdoor for adding unvalidated objects.
Parameters:
map - the map to predicate, must not be null
keyPred - the predicate for keys, must not be null
valuePred - the predicate for values, must not be null
Returns:
a predicated map backed by the given map
Throws:
IllegalArgumentException - if the SortedMap or Predicates are null

fixedSizeSortedMap

public static SortedMap fixedSizeSortedMap(SortedMap map)
Returns a fixed-sized sorted map backed by the given sorted map. Elements may not be added or removed from the returned map, but existing elements can be changed (for instance, via the Map.put(Object,Object) method).
Parameters:
map - the map whose size to fix, must not be null
Returns:
a fixed-size map backed by that map
Throws:
IllegalArgumentException - if the SortedMap is null

lazySortedMap

public static SortedMap lazySortedMap(SortedMap map,
                                      Factory factory)
Returns a "lazy" sorted map whose values will be created on demand.

When the key passed to the returned map's Map.get(Object) method is not present in the map, then the factory will be used to create a new object and that object will become the value associated with that key.

For instance: 

 Factory factory = new Factory() {
     public Object create() {
         return new Date();
     }
 }
 SortedMap lazy = MapUtils.lazySortedMap(new TreeMap(), factory);
 Object obj = lazy.get("test");
After the above code is executed, obj will contain a new Date instance. Furthermore, that Date instance is the value for the test key.
Parameters:
map - the map to make lazy, must not be null
factory - the factory for creating new objects, must not be null
Returns:
a lazy map backed by the given map
Throws:
IllegalArgumentException - if the SortedMap or Factory is null
Overview  Package   Class  Index 
 PREV CLASS   NEXT CLASS FRAMES    NO FRAMES
SUMMARY:  INNER | FIELD | CONSTR | METHOD DETAIL:  FIELD | CONSTR | METHOD
Copyright © 2001-2002 Apache Software Foundation. Documenation generated October 21 2002.