What is the LinkedHashMap.containsValue method in Java?

A LinkedHashMap is same as HashMap, except the LinkedHashMap maintains the insertion order while the HashMap does not.

Internally, the LinkedHashMap uses the doubly-linked list to maintain the insertion order.

Read more about LinkedHashMap here.

What is the containsValue method in LinkedHashMap?

The containsValue method of LinkedHashMap is used to check if the specified value is present in the LinkedHashMap object.

Syntax

public boolean containsValue(Object value)

The value to be checked as present is passed as argument.

This method returns true if the value has one or more keys mapping. Otherwise, false is returned.

Code

The below example shows how to use the containsValue method.

import java.util.LinkedHashMap;
class LinkedHashMapContainsValueExample {
    public static void main( String args[] ) {
      LinkedHashMap<Integer, String> map = new LinkedHashMap<>();
      map.put(1, "one");
      map.put(2, "two");
      System.out.println("\nChecking if the value 'one' is present : "+ map.containsValue("one"));
      System.out.println("\nChecking if the value 'three' is present : "+ map.containsValue("three"));
    }
}

Explanation

In the above code:

  • In line 1, we import the LinkedHashMap class.

  • In line 4, we create a LinkedHashMap object with the name map.

  • In lines 5 and 6, we use the put method to add two mappings ({1=one, 2=two}) to the map object.

  • In line 7, we use the containsValue method to check if the map has a key mapping for the value "one". true is returned as a result because the key 1 is mapped to the value "one"

  • In line 8, we use the containsValue method to check if the map has a key mapping for the value "three". false is returned as a result because the no key is mapped to the value "three".

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