Java中的TreeMap ceilingEntry（）和ceilingKey（）方法-yiteyi-C++库

有二 Java中ceilingEntry（）的变体。util。TreeMap，本文将讨论这两种方法。

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1.ceilingEntry（K键）： 它用于返回 键值映射 与 大于或等于给定密钥的最小密钥， 如果没有这样的密钥，则返回null。

Syntax : 
public Map.Entry ceilingEntry(K key)
Parameters : 
key : The key to be matched.
Return Value : 
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.天花板键（K键）： 这也有同样的工作，作为上面的一个，但唯一的区别是 它不包含映射的键 。它只返回大于或等于给定密钥的最小密钥，否则返回NULL。

Syntax : 
public K ceilingKey(K key)
Parameters : 
key : The key to be matched.
Return Value : 
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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