Java-如何从 HashMap 创建 Java Hashtable

Question

我想从 HashMap 创建 Java 哈希表。

 HashMap hMap = new HashMap();       
//populate HashMap
hMap.put("1","One");
hMap.put("2","Two");
hMap.put("3","Three");

//create new Hashtable
Hashtable ht = new Hashtable();

//populate Hashtable
ht.put("1","This value would be REPLACED !!");
ht.put("4","Four");

在此之后，最简单的程序是什么？

Answer 1

使用接受 Map 的 Hashtable 构造函数:

public Hashtable(Map<? extends K, ? extends V> t) 

此外，在声明 Map 实例时，您应该优先考虑原始类型和接口(interface)编程的泛型类型:

Map<String,String> hMap = new HashMap<>();       
//populate HashMap
hMap.put("1","One");
hMap.put("2","Two");
hMap.put("3","Three");

//create new Hashtable
Map<String,String> ht = new Hashtable<>(hMap);