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;
}
@Test
public 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}