Java程序在Hashtable中使用枚举读取元素

Java中的枚举 是预定义的接口之一，其对象仅用于从集合框架变量（如 Stack、Vector、HashTable 等）中向前检索数据，而不是向后检索。

HashTable 是一个类 哈希表类实现了一个 Map，它将键映射到值。它将键/值对存储在哈希表中。在这个数据结构中，我们指定了一个用作键的对象，以及我们想要与该键关联的值。然后对键进行散列，所得散列代码用作将值存储在表中的索引。 HashMap 不提供任何枚举，而 HashTable 提供非快速失败的枚举。哈希表的层次结构如下：

句法：

public class Hashtable extends Dictionary implements Map, Cloneable, Serializable

参数：

• K：插入的键。
• V：分配给键的值。

为了创建哈希表，从Java.util.Hashtable 导入哈希表，其中 K、V 是整数、字符串、浮点数等数据类型。

语法：创建哈希表

Hashtable ht = new Hashtable();

实施：大学生信息

例子

Java

// Java Program to read elements
// using enumeration in hashtable
 
// Importing enumeration class
import java.util.Enumeration;
// Importing hash table
import java.util.Hashtable;
 
// Class
public class GFG {
 
    // Main driver method
    public static void main(String a[])
    {
 
        // Creating hash table
        Hashtable hm
            = new Hashtable();
 
        // Add key-value pair to Hashtable
        // Custom inputs
        hm.put("Name", "Bahubali");
        hm.put("College", "Amarnath");
        hm.put("Department", "Vedics");
 
        // enum
        Enumeration keys = hm.keys();
 
        // Condition check whether element(K,V) is present
        // using hasMoreElements()
        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
 
            // Print corresponding key-value pair
            System.out.println("Value of " + key
                               + " is: " + hm.get(key));
        }
 
        System.out.println();
 
        // Creating a new Hashtable
        Hashtable hm1
            = new Hashtable();
 
        // Adding key-value pair to Hashtable
        // Custom inputs
        hm1.put("Name", "Ravaan");
        hm1.put("College", "SriLanka");
        hm1.put("Department", "CS");
 
        // Enum
        Enumeration keys1 = hm1.keys();
 
        // Condition check whether element(K,V) is present
        // using hasMoreElements()
        while (keys1.hasMoreElements()) {
            String key = keys1.nextElement();
 
            // Print corresponding key-value pair
            System.out.println("Value of " + key
                               + " is: " + hm1.get(key));
        }
 
        System.out.println();
 
        // Creating a new Hashtable
        Hashtable hm2
            = new Hashtable();
 
        // Adding key-value pair to Hashtable
        // Custom inputs
        hm2.put("Name", "Kattappa");
        hm2.put("College", "Beardo");
        hm2.put("Department", "War");
 
        /// enum
        Enumeration keys2 = hm2.keys();
 
        // Condition check whether element(K,V) is present
        // using hasMoreElements()
        while (keys2.hasMoreElements()) {
            String key = keys2.nextElement();
 
            // Print corresponding key-value pair
            System.out.println("Value of " + key
                               + " is: " + hm2.get(key));
        }
    }
}

输出

Value of Name is: Bahubali
Value of College is: Amarnath
Value of Department is: Vedics

Value of Name is: Ravaan
Value of College is: SriLanka
Value of Department is: CS

Value of Name is: Kattappa
Value of College is: Beardo
Value of Department is: War