Java Collections emptyNavigableSet()

emptyNavigableSet() 获取不可变的空NavigableSet。

1 语法

public static <E> NavigableSet<E> emptyNavigableSet()      

2 参数

无

3 返回值

返回不可变的空NavigableSet。

4 Collections emptyNavigableSet()示例1

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Collections.emptyNavigableSet的例子
 */
import java.util.*;

public class Demo {

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

输出结果为：

Empty Navigable Set: []

5 Collections emptyNavigableSet()示例2

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Collections.emptyNavigableSet的例子
 */
import java.util.*;

public class Demo {

    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");
    }
}

输出结果为：

Exception in thread "main" java.lang.UnsupportedOperationException
Created empty immutable Navigable Set: []
	at java.util.Collections$UnmodifiableCollection.add(Collections.java:1055)
	at com.yiidian.Demo.main(Demo.java:18)

6 Collections emptyNavigableSet()示例3

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
/**
 * Java Collections.emptyNavigableSet的例子
 */
import java.util.*;

public class Demo {

    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);
    }
}

输出结果为：

Exception in thread "main" java.lang.UnsupportedOperationException
	at java.util.Collections$UnmodifiableCollection.add(Collections.java:1055)
	at com.yiidian.Demo.main(Demo.java:16)