Java中的TreeMap size（）方法及其示例-yiteyi-C++库

size（）方法 树映射类 用于获取映射的大小，该大小表示映射中键值对或映射的数量。

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--> java.util package    --> TreeMap class        --> size() Method

语法：

Tree_Map.size()

返回值： 映射的大小，这也意味着映射中存在的键值对的数量。

例1： 将字符串值映射到整数键

JAVA

                         // Java Program to Illustrate size() Method                       
                         // of TreeMap class                       
           
                         // Importing required classes                       
                         import                                     java.util.*;                       
           
                         // Main class                       
                         public                                     class                                     GFG {                       
           
                                                 // Main driver method                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 // Creating an empty TreeMap by                       
                                                 // declaring object of Integer, string pairs                       
                                                 TreeMap<Integer, String> tree_map                       
                                                 =                                     new                                     TreeMap<Integer, String>();                       
           
                                                 // Mapping string values to int keys                       
                                                 // using put() method                       
                                                 tree_map.put(                                     10                                     ,                                     "Geeks"                                     );                       
                                                 tree_map.put(                                     15                                     ,                                     "4"                                     );                       
                                                 tree_map.put(                                     20                                     ,                                     "Geeks"                                     );                       
                                                 tree_map.put(                                     25                                     ,                                     "Welcomes"                                     );                       
                                                 tree_map.put(                                     30                                     ,                                     "You"                                     );                       
           
                                                 // Displaying the elements of TreeMap                       
                                                 System.out.println(                                     "Initial Mappings are: "                       
                                                 + tree_map);                       
           
                                                 // Now displaying the size of this map                       
                                                 // using size() method                       
                                                 System.out.println(                                     "The size of the map is "                       
                                                 + tree_map.size());                       
                                                 }                       
                         }                       

输出：

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}The size of the map is 5

例2： 将整数值映射到字符串键

JAVA

                         // Java Program to Illustrate the size() method                       
                         // of TreeMap class                       
           
                         // Importing required classes                       
                         import                                     java.util.*;                       
           
                         // Main class                       
                         public                                     class                                     GFG {                       
           
                                                 // Main driver method                       
                                                 public                                     static                                     void                                     main(String[] args)                       
                                                 {                       
                                                 // Creating an empty TreeMap by                       
                                                 // declaring object of string, integer pairs                       
                                                 TreeMap<String, Integer> tree_map                       
                                                 =                                     new                                     TreeMap<String, Integer>();                       
           
                                                 // Mapping int values to string keys                       
                                                 // using put() method                       
                                                 tree_map.put(                                     "Geeks"                                     ,                                     10                                     );                       
                                                 tree_map.put(                                     "4"                                     ,                                     15                                     );                       
                                                 tree_map.put(                                     "Geeks"                                     ,                                     20                                     );                       
                                                 tree_map.put(                                     "Welcomes"                                     ,                                     25                                     );                       
                                                 tree_map.put(                                     "You"                                     ,                                     30                                     );                       
           
                                                 // Printing the elements of TreeMap                       
                                                 System.out.println(                                     "Initial Mappings are: "                       
                                                 + tree_map);                       
           
                                                 // Printing the size of the map                       
                                                 // using size() method                       
                                                 System.out.println(                                     "The size of the map is "                       
                                                 + tree_map.size());                       
                                                 }                       
                         }                       

输出：

Initial Mappings are: {4=15, Geeks=20, Welcomes=25, You=30}The size of the map is 4

注：相同的操作可以在不同数据类型的变化和组合的任何类型的映射中执行。

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