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    java.util.HashMap.containsValue() 方法用于检查特定值是由HashMap中的单个键还是多个键映射。它将Value作为参数,如果该值由映射中的任何键映射,则返回True。

    HashMap.containsValue() 句法:

    Hash_Map.containsValue(Object Value)

    参数:该方法只接受一个参数Value类型的Object,并引用其映射应该由map中的任何键检查的值。

    返回值:如果检测到值的映射,则该方法返回布尔值true,否则返回false。

    下面的程序用于说明java.util.HashMap.containsValue()的工作方法

    HashMap.containsValue() 程序1:将字符串值映射到整数键。

    // Java code to illustrate the containsValue() method
    import java.util.*;
    
    public class Hash_Map_Demo {
        public static void main(String[] args)
        {
    
            // Creating an empty HashMap
            HashMap<Integer, String> hash_map = new HashMap<Integer, String>();
    
            // Mapping string values to int keys
            hash_map.put(10, "Geeks");
            hash_map.put(15, "4");
            hash_map.put(20, "Geeks");
            hash_map.put(25, "Welcomes");
            hash_map.put(30, "You");
    
            // Displaying the HashMap
            System.out.println("Initial Mappings are: " + hash_map);
    
            // Checking for the Value 'Geeks'
            System.out.println("Is the value 'Geeks' present? " +
            hash_map.containsValue("Geeks"));
    
            // Checking for the Value 'World'
            System.out.println("Is the value 'World' present? " +
            hash_map.containsValue("World"));
        }
    }
    

    输出:

    Initial Mappings are: {20=Geeks, 25=Welcomes, 10=Geeks, 30=You, 15=4}
    Is the value 'Geeks' present? true
    Is the value 'World' present? false

    HashMap.containsValue()程序2:将整数值映射到字符串键。

    // Java code to illustrate the containsValue() method
    import java.util.*;
    
    public class Hash_Map_Demo {
        public static void main(String[] args)
        {
    
            // Creating an empty HashMap
            HashMap<String, Integer> hash_map = new HashMap<String, Integer>();
    
            // Mapping int values to string keys
            hash_map.put("Geeks", 10);
            hash_map.put("4", 15);
            hash_map.put("Geeks", 20);
            hash_map.put("Welcomes", 25);
            hash_map.put("You", 30);
    
            // Displaying the HashMap
            System.out.println("Initial Mappings are: " + hash_map);
    
            // Checking for the Value '10'
            System.out.println("Is the value '10' present? " +
            hash_map.containsValue(10));
    
            // Checking for the Value '30'
            System.out.println("Is the value '30' present? " +
            hash_map.containsValue(30));
    
            // Checking for the Value '40'
            System.out.println("Is the value '40' present? " +
            hash_map.containsValue(40));
        }
    }
    

    输出:

    Initial Mappings are: {4=15, Geeks=20, You=30, Welcomes=25}
    Is the value '10' present? false
    Is the value '30' present? true
    Is the value '40' present? false

    注意:对于具有不同数据类型的变体和组合的任何类型的映射,都可以执行相同的操作。

     
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