HashMap 和 HashTable区别
HashMap 非线程安全的
HashTable线程安全的
package Collections.Map;import java.util.HashMap;public class HashMapTest {public static void main(String[] args) {HashMap<String,String> map = new HashMap<String,String>();//测试覆盖【值被覆盖】map.put("a", "apple");map.put("a", "animal");System.out.println(map.get("a"));//测试键为空值【键可以为空】map.put(null, "desk");System.out.println(map.values());//测试值为空【值为空】map.put("b", null);System.out.println(map.keySet());//null可以做为键}}
package Collections.Map;import java.util.Hashtable;public class HashTableTest {public static void main(String[] args) {Hashtable<String,String> table = new Hashtable<String,String>();table.put("a", "apple");table.put("a", "animal");System.out.println(table.get("a"));table.put(null, "desk");System.out.println(table.values());table.put("b", null);System.out.println(table.keySet());}}HashMap 可以将key或value设为null
HashTable不能将key或value设为null