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  • 2018-09-26  08:31:11        
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    Java中Hashtable类的java.util.Hashtable.containsValue()方法用于检查特定值是由Hashtable中的单个键还是多个键映射。它将Value作为参数,如果该值由表中的任何键映射,则返回True。

    句法:

    Hash_Table.containsValue(Object Value)

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

    返回值:如果值映射到Hashtable中的任何键,则该方法返回boolean true,否则返回false。

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

    程序1:

    // Java code to illustrate the containsValue() method
    import java.util.*;
     
    public class Hash_Table_Demo {
        public static void main(String[] args)
        {
     
            // Creating an empty Hashtable
            Hashtable<Integer, String> hash_table = 
            new Hashtable<Integer, String>();
     
            // Putting values in the table
            hash_table.put(10, "Geeks");
            hash_table.put(15, "4");
            hash_table.put(20, "Geeks");
            hash_table.put(25, "Welcomes");
            hash_table.put(30, "You");
     
            // Displaying the Hashtable
            System.out.println("Initial Table is: " + hash_table); 
     
            // Checking for the Value 'Geeks'
            System.out.println("Is the value 'Geeks' present? " + 
            hash_table.containsValue("Geeks"));
     
            // Checking for the Value 'World'
            System.out.println("Is the value 'World' present? " + 
            hash_table.containsValue("World"));
        }
    }
    

    输出:

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

    程序2:

    // Java code to illustrate the containsValue() method
    import java.util.*;
     
    public class Hash_Table_Demo {
        public static void main(String[] args)
        {
     
            // Creating an empty Hashtable
            Hashtable<String, Integer> hash_table = 
            new Hashtable<String, Integer>();
     
            // Putting values in the table
            hash_table.put("Geeks", 10);
            hash_table.put("4", 15);
            hash_table.put("Geeks", 20);
            hash_table.put("Welcomes", 25);
            hash_table.put("You", 30);
     
            // Displaying the Hashtable
            System.out.println("Initial Table is: " + hash_table); 
     
            // Checking for the Value '10'
            System.out.println("Is the value '10' present? " + 
            hash_table.containsValue(10));
     
            // Checking for the Value '30'
            System.out.println("Is the value '30' present? " + 
            hash_table.containsValue(30));
     
            // Checking for the Value '40'
            System.out.println("Is the value '40' present? " + 
            hash_table.containsValue(40));
        }
    }
    

    输出:

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

    注意:可以使用任何类型的变体和不同数据类型的组合执行相同的操作。

     

     
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