Java TreeMap ceilingEntry()、ceilingKey()用法及代码示例

Java.util.TreeMap中有ceilingEntry()的两个变体，本文都将进行讨论。

1. ceilingEntry(K Key)：用于返回与大于或等于给定键的最小键关联的键值映射，如果没有这样的键，则返回null。

用法：
public Map.Entry ceilingEntry(K key)
参数：
key: The key to be matched.
返回值：
It returns the entry with the least key greater than or equal to key, and null if 
there is no such key.
Exception:
ClassCastException: It throws the exception if the specified key cannot be compared
with the keys currently in the map.
NullPointerException: It throws the exception if the specified key is null.

// Java code to demonstrate the working of  
// ceilingEntry() 
  
import java.io.*; 
import java.util.*; 
  
public class ceilingEntry1 { 
      
  public static void main(String[] args) { 
   
  // Declaring the tree map of Integer and String 
  TreeMap<Integer, String> treemap = new TreeMap<Integer, String>(); 
       
  // assigning the values in the tree map 
  // using put() 
  treemap.put(2, "two"); 
  treemap.put(7, "seven"); 
  treemap.put(3, "three"); 
     
  // Use of ceilingEntry() 
  // returns 7=seven ( next greater key-value) 
  System.out.println("The next greater key-value of 5 is:" + treemap.ceilingEntry(5)); 
    
  // returns "null" as no value present 
  // greater than or equal to number 
  System.out.println("The next greater key-value of 8 is:" + treemap.ceilingEntry(8)); 
    
  } 
}

输出：

The next greater key-value of 5 is:7=seven
The next greater key-value of 8 is:null

2. ceilingKey(K key)：它与上一个 key 具有相同的工作，但唯一的不同是它不包含mapped-keys。它仅返回大于或等于给定 key 的最小 key ，否则返回NULL。。

用法：
public K ceilingKey(K key)
参数：
key: The key to be matched.
返回值：
It returns the entry with the least key greater than or equal to key, and null 
if there is no such key.
Exception:
ClassCastException: It throws the exception if the specified key cannot be compared
with the keys currently in the map.
NullPointerException: It throws the exception if the specified key is null.

// Java code to demonstrate the working of  
// ceilingKey() 
  
import java.io.*; 
import java.util.*; 
  
public class ceilingKey1 { 
      
  public static void main(String[] args) { 
   
  // Declaring the tree map of Integer and String 
  TreeMap<Integer, String> treemap = new TreeMap<Integer, String>(); 
       
  // assigning the values in the tree map 
  // using put() 
  treemap.put(2, "two"); 
  treemap.put(7, "seven"); 
  treemap.put(3, "three"); 
     
  // Use of ceilingKey() 
  // returns 7 ( next greater key) 
  System.out.println("The next greater key of 5 is:" + treemap.ceilingKey(5)); 
    
  // returns "null" as no key present 
  // greater than or equal to number 
  System.out.println("The next greater key of 8 is:" + treemap.ceilingKey(8)); 
    
  } 
}

输出：

The next greater key of 5 is:7
The next greater key of 8 is:null

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注：本文由纯净天空筛选整理自 TreeMap ceilingEntry() and ceilingKey() methods in Java。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。