The java.util.concurrent.ConcurrentHashMap.containsValue() method is an in-built function in Java which accepts a value and returns true if one or more keys are mapped to the specified value. This method traverses the entire hashtable. Thus it is a much slower function than containsKey() method.
Syntax:
chm.containsValue(Object val_element)
Parameters: The method accepts a single parameter val_element of object type which is to be checked for whether it is mapped to any key in the map or not.
Return Value: The method returns true if the specified val_element is mapped to any key in this map and false otherwise.
Exception: The function throws NullPointerException when the specified value_element is null.
Below programs illustrate the use of java.util.concurrent.ConcurrentHashMap.containsValue() method :
Program 1: This program involves mapping Integer Values to String Keys.
/* Java Program to demonstrate containsValue() method of ConcurrentHashMap */ import java.util.concurrent.*; class ConcurrentHashMapDemo { public static void main(String[] args) { ConcurrentHashMap<String, Integer> chm = new ConcurrentHashMap<String, Integer>(); chm.put( "Geeks" , 120 ); chm.put( "for" , 11 ); chm.put( "GeeksforGeeks" , 15 ); chm.put( "Gfg" , 50 ); chm.put( "GFG" , 25 ); // Check whether a key is mapped to 100 if (chm.containsValue( 100 )) { System.out.println( "100 is mapped." ); } else { System.out.println( "100 is not mapped." ); } // Check whether a key is mapped to 120 if (chm.containsValue( 120 )) { System.out.println( "120 is mapped." ); } else { System.out.println( "120 is not mapped." ); } } } |
100 is not mapped. 120 is mapped.
Program 2: This program involves mapping String Values to Integer Keys.
/* Java Program to demonstrate containsValue() method of ConcurrentHashMap */ import java.util.concurrent.*; class ConcurrentHashMapDemo { public static void main(String[] args) { ConcurrentHashMap<Integer, String> chm = new ConcurrentHashMap<Integer, String>(); chm.put( 100 , "Geeks" ); chm.put( 101 , "for" ); chm.put( 102 , "Geeks" ); chm.put( 103 , "Gfg" ); chm.put( 104 , "GFG" ); // Check whether a key is mapped to Geeks if (chm.containsValue( "Geeks" )) { System.out.println( "Geeks is mapped." ); } else { System.out.println( "Geeks is not mapped." ); } // Check whether a key is mapped to GfG if (chm.containsValue( "GfG" )) { System.out.println( "GfG is mapped." ); } else { System.out.println( "GfG is not mapped." ); } } } |
Geeks is mapped. GfG is not mapped.
Reference : https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentHashMap.html#containsValue()
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