Java ConcurrentHashMap | clear（）-yiteyi-C++库

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clear（）方法 爪哇。util。concurrentHashMap。clear（）方法用于清除映射。它用于从ConcurrentHashMap中删除映射。

语法：

public void clear()

                     // Java program to demonstrate                   
                     // clear() method                   
                             
                     import                               java.util.concurrent.ConcurrentHashMap;                   
                     import                               java.util.*;                   
                             
                     public                               class                               ConcurrentHashMapExample {                   
                             
                                         public                               static                               void                               main(String[] args)                   
                                         {                   
                             
                                         // Creating a ConcurrentHashMap                   
                                         Map<String, String> my_cmmap =                               new                               ConcurrentHashMap<String, String>();                   
                             
                                         // Inserting mappings in ConcurrentHashMap                   
                                         // with the help of put() method                   
                                         my_cmmap.put(                               "1"                               ,                               "1"                               );                   
                                         my_cmmap.put(                               "2"                               ,                               "1"                               );                   
                                         my_cmmap.put(                               "3"                               ,                               "1"                               );                   
                                         my_cmmap.put(                               "4"                               ,                               "1"                               );                   
                                         my_cmmap.put(                               "5"                               ,                               "1"                               );                   
                                         my_cmmap.put(                               "6"                               ,                               "1"                               );                   
                             
                                         // Print the ConcurrentHashMap                   
                                         System.out.println(                               "Map before use of clear(): "                   
                                         + my_cmmap);                   
                             
                                         // Now clear the map using clear()                   
                                         my_cmmap.clear();                   
                             
                                         // Print the clea Map                   
                                         System.out.println(                               "Map after use of clear(): "                   
                                         + my_cmmap);                   
                                         }                   
                     }                   

输出：

Map before use of clear(): 
{1=1, 2=1, 3=1, 4=1, 5=1, 6=1}
Map after use of clear(): {}

例2：

                     // Java program to demonstrate                   
                     // clear() method                   
                             
                     import                               java.util.concurrent.ConcurrentHashMap;                   
                     import                               java.util.*;                   
                             
                     public                               class                               ConcurrentHashMapExample {                   
                             
                                         public                               static                               void                               main(String[] args)                   
                                         {                   
                                         // Creating a ConcurrentHashMap                   
                                         Map<String, String> my_map =                               new                               ConcurrentHashMap<String, String>();                   
                             
                                         // Inserting mappings in ConcurrentHashMap                   
                                         // with the help of put() method                   
                                         my_map.put(                               "Geeks"                               ,                               "100"                               );                   
                                         my_map.put(                               "Geek2"                               ,                               "150"                               );                   
                                         my_map.put(                               "Geeks3"                               ,                               "120"                               );                   
                                         my_map.put(                               "Geek4"                               ,                               "111"                               );                   
                                         my_map.put(                               "Geek5"                               ,                               "110"                               );                   
                                         my_map.put(                               "Geek6"                               ,                               "100"                               );                   
                             
                                         // Print the ConcurrentHashMap                   
                                         System.out.println(                               "Map before use of clear(): "                   
                                         + my_map);                   
                             
                                         // Now clear the map using clear()                   
                                         my_map.clear();                   
                             
                                         // Print the cleared Map                   
                                         System.out.println(                               "Map after use of clear(): "                   
                                         + my_map);                   
                                         }                   
                     }                   

输出：

Map before use of clear(): 
{Geeks3=120, Geek6=100, Geek5=110, Geek4=111, Geeks=100, Geek2=150}
Map after use of clear(): {}

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