Java Collections enumeration()方法及示例

java.util.Collections 类的 enumeration() 方法是用来返回指定集合的枚举。这提供了与需要枚举作为输入的传统API的互操作性。
语法：

public static  Enumeration enumeration(Collection c)

参数： 该方法以集合 c 为参数，将返回一个枚举。

返回值： 该方法返回指定集合上的一个 枚举 。

下面是说明enumeration()方法的例子

例1：

// Java program to demonstrate
// enumeration() method
// for String value
 
import java.util.*;
 
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
 
            // creating object of List<String>
            List<String> arrlist = new ArrayList<String>();
 
            // Adding element to srclst
            arrlist.add("Ram");
            arrlist.add("Gopal");
            arrlist.add("Verma");
 
            // Print the list
            System.out.println("List: " + arrlist);
 
            // creating object of type Enumeration<String>
            Enumeration<String> e = Collections.enumeration(arrlist);
 
            // Print the Enumeration
            System.out.println("\nEnumeration over list: ");
 
            // print the enumeration
            while (e.hasMoreElements())
                System.out.println("Value is: " + e.nextElement());
        }
 
        catch (IllegalArgumentException e) {
            System.out.println("Exception thrown : " + e);
        }
 
        catch (NoSuchElementException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

List: [Ram, Gopal, Verma]

Enumeration over list: 
Value is: Ram
Value is: Gopal
Value is: Verma

例2：

// Java program to demonstrate
// enumeration() method
// for Integer value
 
import java.util.*;
 
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
 
            // creating object of List<Integer>
            List<Integer> arrlist = new ArrayList<Integer>();
 
            // Adding element to srclst
            arrlist.add(20);
            arrlist.add(30);
            arrlist.add(40);
 
            // Print the list
            System.out.println("List: " + arrlist);
 
            // creating object of type Enumeration<Integer>
            Enumeration<Integer> e = Collections.enumeration(arrlist);
 
            // Print the Enumeration
            System.out.println("\nEnumeration over list: ");
 
            // print the enumeration
            while (e.hasMoreElements())
                System.out.println("Value is: " + e.nextElement());
        }
 
        catch (IllegalArgumentException e) {
            System.out.println("Exception thrown : " + e);
        }
 
        catch (NoSuchElementException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出

List: [20, 30, 40]

Enumeration over list: 
Value is: 20
Value is: 30
Value is: 40