Java Collections list()方法及实例

java.util.Collections 类的 list() 方法用于返回一个数组列表，其中包含由指定枚举返回的元素，其顺序是由枚举返回的。这个方法提供了返回枚举的传统API和需要集合的新API之间的互操作性。

语法

public static ArrayList list(Enumeration e)

参数： 该方法以 枚举e 为参数，为返回的数组列表提供元素。

返回值： 该方法返回 一个数组列表 ，包含由指定枚举返回的元素。

下面是说明list()方法的例子

例1 :

// Java program to demonstrate
// list() 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>();
  
            // creating object of Vector<String>
            Vector<String> v = new Vector<String>();
  
            // Adding element to Vector v
            v.add("A");
            v.add("B");
            v.add("C");
            v.add("D");
            v.add("E");
  
            // printing the list
            System.out.println("Current list : " + arrlist);
  
            // creating Enumeration
            Enumeration<String> e = v.elements();
  
            // getting arrlist of specified Enumeration
            // using list() method
            arrlist = Collections.list(e);
  
            // printing the arrlist
            System.out.println("Returned list: " + arrlist);
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出。

Current list : []
Returned list: [A, B, C, D, E]

例2 :

// Java program to demonstrate
// list() method
// for Integer value
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] argv) throws Exception
    {
        try {
  
            // creating object of List<String>
            List<Integer> arrlist = new ArrayList<Integer>();
  
            // creating object of Vector<String>
            Vector<Integer> v = new Vector<Integer>();
  
            // Adding element to Vector v
            v.add(10);
            v.add(20);
            v.add(30);
            v.add(40);
            v.add(50);
  
            // printing the list
            System.out.println("Current list : " + arrlist);
  
            // creating Enumeration
            Enumeration<Integer> e = v.elements();
  
            // getting arrlist of specified Enumeration
            // using list() method
            arrlist = Collections.list(e);
  
            // printing the arrlist
            System.out.println("Returned list: "
                               + arrlist);
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception thrown : " + e);
        }
    }
}

输出。

Current list : []
Returned list: [10, 20, 30, 40, 50]