Java ConcurrentSkipListSet higher()方法

java.util.concurrent.ConcurrentSkipListSet 的 higher(E e) 方法是Java中的一个内置函数，它返回这个集合中严格大于给定元素的最小元素，如果没有这样的元素，则返回null。

语法

public E higher(E e)

参数： 该函数接受一个单一参数e，即要匹配的值。

返回值： 该函数返回大于e的最小元素，如果没有这样的元素，则返回空。

异常： 该函数会抛出以下异常。

• ClassCastException - 如果指定的元素不能与当前集合中的元素进行比较。
• NullPointerException - 如果指定的元素是空的。

下面的程序说明了ConcurrentSkipListSet.higher(E e)方法。

程序1 :

// Java program to demonstrate higher()
// method of ConcurrentSkipListSet
  
import java.util.concurrent.*;
  
class ConcurrentSkipListSetHigherExample1 {
    public static void main(String[] args)
    {
        // Creating a set object
        ConcurrentSkipListSet<Integer>
            Lset = new ConcurrentSkipListSet<Integer>();
  
        // Adding elements to this set
        for (int i = 10; i <= 50; i += 10)
            Lset.add(i);
  
        // Finding higher of 20 in the set
        System.out.println("The higher of 20 in the set: "
                           + Lset.higher(20));
  
        // Finding higher of 39 in the set
        System.out.println("The higher of 39 in the set: "
                           + Lset.higher(39));
  
        // Finding higher of 50 in the set
        System.out.println("The higher of 50 in the set: "
                           + Lset.higher(50));
    }
}

输出:

The higher of 20 in the set: 30
The higher of 39 in the set: 40
The higher of 50 in the set: null

程序2： 显示 higher()中NullPointerException的程序。

// Java program to demonstrate higher()
// method of ConcurrentSkipListSet
  
import java.util.concurrent.*;
  
class ConcurrentSkipListSetHigherExample1 {
    public static void main(String[] args)
    {
        // Creating a set object
        ConcurrentSkipListSet<Integer>
            Lset = new ConcurrentSkipListSet<Integer>();
  
        // Adding elements to this set
        for (int i = 10; i <= 50; i += 10)
            Lset.add(i);
  
        try {
            // Trying to find higher of "null" in the set
            System.out.println("The higher of null in the set: "
                               + Lset.higher(null));
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

输出:

Exception: java.lang.NullPointerException

参考资料:
https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#higher-E-