Java教程

Java Collections emptyNavigableSet()

Java集合类的 emptyNavigableSet()方法用于获取本质上不可变的空可导航Set。

语法

以下是 emptyNavigableSet()方法的声明:
public static <E> NavigableSet<E> emptyNavigableSet()        

参数

此方法不接受任何参数。

返回

emptyNavigableSet()方法将返回一个不包含元素的不可变导航Set。

异常

NA

兼容版本

Java 1.8及更高版本

示例1

import java.util.*;
public class CollectionsEmptyNavigableSetExample1 {
    public static void main(String[] args) {      
         //Create an empty Set   
         NavigableSet<String> EmpNavSet = Collections.<String>emptyNavigableSet();
         System.out.println("Empty Navigable Set: "+EmpNavSet);
         }    
}   
输出:
Empty Navigable Set: []

示例2

import java.util.*;
public class CollectionsEmptyNavigableSetExample2 {
    public static void main(String[] args) {      
        //Create an empty Navigable Set
          NavigableSet<String> EmpNavSet = Collections.emptyNavigableSet();
          System.out.println("Created empty immutable Navigable Set: "+EmpNavSet);
          //try to add elements
          EmpNavSet.add("A");
          EmpNavSet.add("B");
          }   
}
输出:
Created empty immutable Navigable Set: []
Exception in thread "main" java.lang.UnsupportedOperationException
    at java.base/java.util.Collections$UnmodifiableCollection.add(Collections.java:1056)
    at myPackage.CollectionsEmptyNavigableSetExample2.main(CollectionsEmptyNavigableSetExample2.java:9)

示例3

import java.util.*;
public class CollectionsEmptyNavigableSetExample3 {
    public static void main(String[] args) {      
        //Create an empty Navigable Set   
          Set<Integer> empNavSet = Collections.emptyNavigableSet();
          empNavSet.add(1);
          empNavSet.add(2);    
          System.out.println("Created empty immutable Navigable Set: "+empNavSet);        
          }   
}
输出:
Exception in thread "main" java.lang.UnsupportedOperationException
    at java.base/java.util.Collections$UnmodifiableCollection.add(Collections.java:1056)
    at myPackage.CollectionsEmptyNavigableSetExample3.main(CollectionsEmptyNavigableSetExample3.java:7)

昵称: 邮箱:
Copyright © 2022 立地货 All Rights Reserved.
备案号:京ICP备14037608号-4