虽然这里有很多很好的答案，但我想给出我自己的表，描述与Java 11绑定的各种Map实现。

我们可以在图表中看到这些差异:

HashMap is the general-purpose Map commonly used when you have no special needs. LinkedHashMap extends HashMap, adding this behavior: Maintains an order, the order in which the entries were originally added. Altering the value for key-value entry does not alter its place in the order. TreeMap too maintains an order, but uses either (a) the “natural” order, meaning the value of the compareTo method on the key objects defined on the Comparable interface, or (b) invokes a Comparator implementation you provide. TreeMap implements both the SortedMap interface, and its successor, the NavigableMap interface. NULLs: TreeMap does not allow a NULL as the key, while HashMap & LinkedHashMap do. All three allow NULL as the value. HashTable is legacy, from Java 1. Supplanted by the ConcurrentHashMap class. Quoting the Javadoc: ConcurrentHashMap obeys the same functional specification as Hashtable, and includes versions of methods corresponding to each method of Hashtable.

这三个都表示从唯一键到值的映射，因此实现了Map接口。

HashMap is a map based on hashing of the keys. It supports O(1) get/put operations. Keys must have consistent implementations of hashCode() and equals() for this to work. LinkedHashMap is very similar to HashMap, but it adds awareness to the order at which items are added (or accessed), so the iteration order is the same as insertion order (or access order, depending on construction parameters). TreeMap is a tree based mapping. Its put/get operations take O(log n) time. It requires items to have some comparison mechanism, either with Comparable or Comparator. The iteration order is determined by this mechanism.

哈希映射不保留插入顺序。 的例子。Hashmap 如果您正在插入键作为

1  3
5  9
4   6
7   15
3   10

它可以存储为

4  6
5  9
3  10
1  3
7  15

链接Hashmap保留插入顺序。

的例子。 如果您正在插入键

1  3
5  9
4   6
7   15
3   10

它将存储为

1  3
5  9
4   6
7   15
3   10

和我们插入的一样。

树映射以键的递增顺序存储山谷。 的例子。 如果您正在插入键

1  3
5  9
4   6
7   15
3   10

它将存储为

1  3
3  10
4   6
5   9
7   15

HashMap

它有一对值(键，值) 禁止复制键值 无序的无序 它允许一个空键和多个空值

哈希表

和哈希映射一样 它不允许空键和空值

LinkedHashMap

它是map实现的有序版本 基于链表和哈希数据结构

TreeMap

有序和排序版本 基于哈希数据结构

这些是同一接口的不同实现。每种实现都有一些优点和缺点(快速插入，缓慢搜索)，反之亦然。

有关详细信息，请参阅TreeMap, HashMap, LinkedHashMap的javadoc。

三者中最重要的是如何保存条目的顺序。

HashMap -不保存条目的顺序。 如。

public static void main(String[] args){
        HashMap<String,Integer> hashMap = new HashMap<>();
        hashMap.put("First",1);// First ---> 1 is put first in the map
        hashMap.put("Second",2);//Second ---> 2 is put second in the map
        hashMap.put("Third",3); // Third--->3 is put third in the map
        for(Map.Entry<String,Integer> entry : hashMap.entrySet())
        {
            System.out.println(entry.getKey()+"--->"+entry.getValue());
        }
    }

LinkedHashMap:它保存条目的顺序。例如:

public static void main(String[] args){
        LinkedHashMap<String,Integer> linkedHashMap = new LinkedHashMap<>();
        linkedHashMap.put("First",1);// First ---> 1 is put first in the map
        linkedHashMap.put("Second",2);//Second ---> 2 is put second in the map
        linkedHashMap.put("Third",3); // Third--->3 is put third in the map
        for(Map.Entry<String,Integer> entry : linkedHashMap.entrySet())
        {
            System.out.println(entry.getKey()+"--->"+entry.getValue());
        }
    }

TreeMap:按键的升序保存条目。例如:

public static void main(String[] args) throws IOException {
        TreeMap<String,Integer> treeMap = new TreeMap<>();
        treeMap.put("A",1);// A---> 1 is put first in the map
        treeMap.put("C",2);//C---> 2 is put second in the map
        treeMap.put("B",3); //B--->3 is put third in the map
        for(Map.Entry<String,Integer> entry : treeMap.entrySet())
        {
            System.out.println(entry.getKey()+"--->"+entry.getValue());
        }
    }