java.util.Map

包

package java.util;

简介

An object that maps keys to values. A map cannot contain duplicate keys; each key can map to at most one value.

结构

查询操作

// Query Operations
int size();
boolean isEmpty();
boolean containsKey(Object key);
boolean containsValue(Object value);
V get(Object key);

修改操作

// Modification Operations
V put(K key, V value);
V remove(Object key);

批量操作

// Bulk Operations
void putAll(Map m);
void clear();

查看方法

// Views
Set keySet();
Collection values();
Set> entrySet();

内部类 Entry

K getKey();
V getValue();
V setValue(V value);

比较和哈希

参考文章：
JAVA泛型知识（二）--> 和
JAVA8的java.util.function包

// Comparison and hashing
boolean equals(Object o);
int hashCode();
boolean equals(Object o);
int hashCode();
public static , V> Comparator> comparingByKey();
public static > Comparator> comparingByValue();
public static  Comparator> comparingByKey(Comparator cmp);
public static  Comparator> comparingByValue(Comparator cmp);

默认方法

参考文章：
java接口中的default方法

// Defaultable methods
default V getOrDefault(Object key, V defaultValue);
default void forEach(BiConsumer action);
default void replaceAll(BiFunction function);
default V putIfAbsent(K key, V value);
default boolean remove(Object key, Object value);
default boolean replace(K key, V oldValue, V newValue);
default V replace(K key, V value)
default V computeIfAbsent(K key,
            Function mappingFunction);
default V computeIfPresent(K key,
            BiFunction remappingFunction);
default V computeIfPresent(K key,
            BiFunction remappingFunction);
default V compute(K key,
            BiFunction remappingFunction);
default V merge(K key, V value,
            BiFunction remappingFunction)