Java 中的 ConcurrentSkipListSet floor()方法
原文:https://www . geeksforgeeks . org/concurrentskiplistset-floor-in-method-Java/
java . util . concurrentSkiplistset的 floor() 方法是 Java 中的一个内置函数，它返回该集合中小于或等于给定元素的最大元素，如果没有这样的元素，则返回 null。
语法:
ConcurrentSkipListSet.floor(E e)
参数:该函数接受单个参数 e ，即要匹配的值。
返回值:该函数返回小于或等于 e 的最大元素，如果没有该元素，则返回空值。
异常:函数抛出以下异常:
-
class castexception–如果指定元素无法与集合中的当前元素进行比较。 NullPointerException* – if the specified element is null
下面的程序说明了 ConcurrentSkipListSet.floor()方法:
程序 1:
```java // Java program to demonstrate floor() // method of ConcurrentSkipListSet
import java.util.concurrent.*;
class ConcurrentSkipListSetFloorExample1 { public static void main(String[] args) { // Creating a set object ConcurrentSkipListSet Lset = new ConcurrentSkipListSet();
// Adding elements to this set for (int i = 10; i <= 50; i += 10) Lset.add(i);
// Finding floor of 20 in the set System.out.println("The floor of 20 in the set " + Lset.floor(20));
// Finding floor of 39 in the set System.out.println("The floor of 39 in the set " + Lset.floor(39));
// Finding floor of 9 in the set System.out.println("The floor of 10 in the set " + Lset.floor(9)); } } ```
Output:
```java The floor of 20 in the set 20 The floor of 39 in the set 30 The floor of 10 in the set null
```
程序 2: 在楼层()显示空指针异常的程序。
```java // Java program to demonstrate floor() // method of ConcurrentSkipListSet
import java.util.concurrent.*;
class ConcurrentSkipListSetFloorExample2 { public static void main(String[] args) { // Creating a set object ConcurrentSkipListSet Lset = new ConcurrentSkipListSet();
// Adding elements to this set for (int i = 10; i <= 50; i += 10) Lset.add(i);
// Trying to find the floor of null try { System.out.println("The floor of null in the set " + Lset.floor(null)); } catch (Exception e) { System.out.println("Exception: " + e); } } } ```
Output:
```java Exception: java.lang.NullPointerException
```
参考:https://docs . Oracle . com/javase/8/docs/API/Java/util/concurrentskiplistset . html # floor-E-
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