JAVAutil。树地图。Java中的containskey（）和containsValue（）-yiteyi-C++库

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

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1.containskey（对象o）： 如果映射包含指定键的映射，则返回true。

Parameters:
o : The key which will be tested whether present or not.
Return Value:
Returns true if there is a mapping for the given key.
Exception:
ClassCastException : This is thrown if the given key cannot be compared
with the keys currently in the map.
NullPointerException : This is thrown if the specified key is null.

                     // Java code to demonstrate the working                   
                     // of containsKey()                   
                             
                     import                               java.io.*;                   
                     import                               java.util.*;                   
                             
                     public                               class                               containsKey {                   
                     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"                               );                   
                                         treemap.put(                               6                               ,                               "six"                               );                   
                                         treemap.put(                               9                               ,                               "nine"                               );                   
                             
                                         // Use of containsKey                   
                                         // returns true if mapping for the number is present                   
                                         System.out.println(treemap.containsKey(                               6                               ));                   
                                         System.out.println(treemap.containsKey(                               4                               ));                   
                                         }                   
                     }                   

输出：

true
false

2.包含值（对象o）： 如果此映射将一个或多个键映射到指定值，则返回true。

Parameters:
o : This is the value whose presence in this map is to be tested.
Return Value:
Returns true if a mapping to this value exists else false.
Exception:
NA

                     // Java code to demonstrate the working                   
                     // of containsValue()                   
                             
                     import                               java.io.*;                   
                     import                               java.util.*;                   
                             
                     public                               class                               containsValue {                   
                     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"                               );                   
                                         treemap.put(                               6                               ,                               "six"                               );                   
                                         treemap.put(                               9                               ,                               "nine"                               );                   
                             
                                         // Use of containsValue                   
                                         // returns true if more than one keys are mapped                   
                                         System.out.println(treemap.containsValue(                               "six"                               ));                   
                                         System.out.println(treemap.containsValue(                               "four"                               ));                   
                                         }                   
                     }                   