当哈希表的大小为素数时,简单的取模哈希的结果会更加均匀。 而HashMap则更加关注hash的计算效率问题。在取模计算时,如果模数是2的幂,那么我们可以直接使用位运算来得到结果,效率要大大高于做除法。当 length 总是2的n次方时,hash & (length-1)运算等价于对 length 取模,也就是 hash%length,但是&比%具有更高...
首先看一下官网的推荐 1* Java Collections Framework</a>. Unlike thenewcollection2* implementations, {@code Hashtable} issynchronized. If a3* thread-safe implementation is not needed, it is recommended to use4* {@link HashMap} in place of {@code Hashtable}. If a thread-safe5* highly-con...
As of the Java 2 platform v1.2, this class has been retrofitted to implement Map, so that it becomes a part of Java's collection framework. Unlike the new collection implementations, Hashtable is synchronized. The iterators returned by theiteratormethod of the collections returned by all of th...
Java 实例以下实例演示了如何使用 Enumeration 类的 hasMoreElements 和 nextElement 方法来遍历输出 HashTable 中的内容:Main.java 文件 import java.util.Enumeration; import java.util.Hashtable; public class Main { public static void main(String[] args) { Hashtable ht = new Hashtable(); ht.put("...
Java Collections Framework. Unlike the new collection implementations, Hashtable is synchronized. If a thread-safe implementation is not needed, it is recommended to use HashMap in place of Hashtable. If a thread-safe highly-concurrent implementation is desired, then it is recommended to use java...
= (Integer)numbers.get("two"); * if (n != null) { * System.out.println("two = " + n); * } * </pre></blockquote> * <p> * As of the Java 2 platform v1.2, this class has been retrofitted to * implement Map, so that it becomes a part of Java's collection framework. ...
Java容器类Collection、List、ArrayList、Vector及map、HashTable、HashMap区别 Collection是List和Set两个接口的基接口 List在Collection之上增加了"有序" Set在Collection之上增加了"唯一" 而ArrayList是实现List的类...所以他是有序的. 它里边存放的元素在排列上存在一定的先后顺序 ...
Java 实例以下实例演示了如何使用 Enumeration 类的 hasMoreElements 和 nextElement 方法来遍历输出 HashTable 中的内容:Main.java 文件 import java.util.Enumeration; import java.util.Hashtable; public class Main { public static void main(String[] args) { Hashtable ht = new Hashtable(); ht.put("...
Java HashTable compute()方法及示例Hashtable类的 compute(Key, BiFunction) 方法允许为指定的键和其当前的映射值计算一个映射(如果没有找到当前的映射,则为空)。如果在Hashtable的compute()中传递的重映射函数的返回值为null,那么该映射将从Hashtable中移除(如果最初没有,则保持不存在)。 如果重映射函数抛出一...
As of the Java 2 platform v1.2, this class was retrofitted to implement theMapinterface, making it a member of the Java Collections Framework. Unlike the new collection implementations,Hashtableis synchronized. If a thread-safe implementation is not needed, it is recommended to useHashMapin plac...