Java基礎|Map常用方法
4995 ワード
Mapの一般的な方法
Entryメソッド
Java 8がMapに追加したメソッド
mapを巡る方法
Map map = new HashMap(); // map
Map iMap = new HashMap();
iMap.put(" "," ")
map.put(" "," "); // , key ,
map.put(" "," ");
map.put(" "," ");
map.put(" "," ");
map.remove(" ") // key , key value, null
map.remove(" "," ") // , true
map.size() // map
map.clear() // map
map.isEmpty() // map
map.get(" ") // Key value, null
map.cotainsKey(" ") // Map Key
map.containsValue(" ") // Map Value
Collection set = map.entrySet() // Map Set. Map.Entry(Map )
Collection set = map.keySet() // Map key set
Collection list = map.values() // Map value Collection
Entryメソッド
//Map Entry,
Collection set = map.entrySet()
set.forEach(entry ->
System.out.println("--->"+obj.getKey()) // entry key
System.out.println("--->"+obj.getValue()) // entry value
obj.setValue(" ") // entry value, value
)
Java 8がMapに追加したメソッド
// remappingFunction value, , ; ;
Object compute(Object key,BiFunction remappingFunction)
map.compute(" ",(key,vlaue)->((String)key).length())
//key value , 。 remappingFunction key value, value null, ;value ,
object computeIfAbsent(object key, Function remappingFunction)
// key value , , value, ,
Object computeIfPresent(object key,BiFunction remappingFunction)
// Map
void forEach(BiFunction action)
map.forEach((k,v)-> System.out.println("key:"+k+" value:"+v));
// key value, key , defaultValue
object getOrDefault(object key,V defalutValue)
System.out.println(map.getOrDefault(" "," "));
// key value, value , remappingFunction value value value, value , key,value . null
Object merge(object key,object value,BiFunction remappingFunction)
// key value , value
object putIfAbsent(Object key,object value)
// key value。 key 。
object replace(object key,object value)
// , true,
boolean replace(K key,V oldValue,V newValue)
// , value
replaceAll(BiFunction function)
map.replaceAll((k,v)->((String)k).length());
mapを巡る方法
for(Object key : map.keySet()){
System.out.printLn(key +"---> "+map.get(key))
}
map.forEach((k,v)-> System.out.println("key:"+k+" value:"+v));