内容

• 是Apache组织下的commons-collections包中的工具类

<dependency><groupId>commons-collections</groupId><artifactId>commons-collections</artifactId><version>3.2.1</version></dependency>

• Map操作相关的，最常用和null值相关

使用

• 取值

public static String getString(final Map map, final Object key) {if (map != null) {Object answer = map.get(key);if (answer != null) {return answer.toString();}}return null;}public static String getString( Map map, Object key, String defaultValue ) {String answer = getString( map, key );if ( answer == null ) {answer = defaultValue;}return answer;}

取值，二元参数无默认字符串；

同样有针对其他类型的取值方法；

• 赋值

putAll()public static void safeAddToMap(Map map, Object key, Object value) throws NullPointerException {if (value == null) {map.put(key, "");} else {map.put(key, value);}}

一个是putAll，数组加入map中；

一个是safeAdd，不加入null值；

• 操作

//排序
public static Map orderedMap(Map map) {return ListOrderedMap.decorate(map);}//反转，key value互换
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;}    

@Testpublic void testMapUtils() {Map<String,String> map = new HashMap<>();map.put("shit","Happens");map.put("0","1");log.info("{}",MapUtils.getString(map,"shi222t","hhhhh"));log.info("order:{}",MapUtils.orderedMap(map));log.info("invert:{}",MapUtils.invertMap(map));}[INFO ] 2018-10-30 14:07:42,144 method:com.andy.dot.TestAllDots.testMapUtils(TestAllDots.java:177)
hhhhh
[INFO ] 2018-10-30 14:07:42,276 method:com.andy.dot.TestAllDots.testMapUtils(TestAllDots.java:178)
order:{0=1, shit=Happens}
[INFO ] 2018-10-30 14:07:42,277 method:com.andy.dot.TestAllDots.testMapUtils(TestAllDots.java:179)
invert:{Happens=shit, 1=0}

参考文章

• MapUtils常用方法
• Class MapUtils