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Java Hashmap containsKey() Method
What is a Hashmap?
Hashmap was first introduced in Java 1.2.The Hashmap class is included in the java.util package.The data in a hashmap is stored in two parts: the key and the value, which can be accessed using an index of another type.A hashmap have unique keys , inserting a duplicate key will replace the data of the key. Hashmap class have many inbuilt method, one of those method is Java Hashmap containsKey() Method.
To know more about Hashmap containsKey() Method read the complete article
Java Hashmap containsKey() Method
The hashmap containsKey() method checks if the hashmap have the mapping of the specified key or not. It takes on parameter. Below in this page you can find it’s syntax, return values, parameters with detailed examples.
Syntax :
hashmap.containsKey(object key);
Parameters :
Object Key: The key whose mapping is to be find.
Return values :
True : If mapping is present. False : If mapping does not present.
Hashmap containsKey() Method Examples
Example :
Run
import java.util.*; public class Main { 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, "Java"); hash_map.put (20, "Hashmap"); hash_map.put (25, "containsKey"); hash_map.put (30, "method"); //retrieving the value mapped to key 5 System.out.println ("key 20 : " + hash_map.containsKey(20)); // retrieving the value mapped to key 5 System.out.println ("key 15 : " + hash_map.containsKey(15)); } } Output :
key 20 : true key 15 : false
What happened above: In the above example a hashmap is created and elements are inserted in the hashmap. When the containsKey(20) method it returns 'true' because it's mapping is present in the hashmap , while containsKey(15) is called it returns 'false' because mapping is not present for key '15'.
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