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Java Hashmap keySet() Method
What is a Hashmap?
Hashmap class is a part of java.util package. In hashmap key/value pairs can be stored , but no duplicate key is allowed.If a duplicate key is inserted it will replace the present value with the new value. Many built-in methods are there in hashmap class which makes it easy to perform operations on them, like insertion , deletion and many more. One of those methods is Java Hashmap keySet() Method.
To know more about Hashmap keySet() Method read the complete article.
Java Hashmap keySet() Method
The hashmap keySet() method is used make a set of keys present in the hashmap. This method returns a set of keys. Below in this page you can find it’s syntax, return values, parameters with detailed examples.
Syntax :
new_hashmap.keySet();
Return values :
This methos returns a set of keys present in the hashmap.
Hashmap keySet() Method Examples
Example :
import java.util.*;
public class Main
{
public static void main (String[]args)
{
// Creating an empty HashMap
HashMap < String, Integer > hash_map_1 =
new HashMap < String, Integer > ();
// Mapping string values to int keys in a empty hashmap
hash_map_1.put ("Maths", 80);
hash_map_1.put ("English", 75);
hash_map_1.put ("Hindi", 85);
hash_map_1.put ("Science", 90);
System.out.println("Original hashmap : " + hash_map_1);
//printing the keys present in hte hashmap
System.out.println("Keys present in the hashmap : "+hash_map_1.keySet());
}
}
Output :
Original hashmap : {Maths=80, English=75, Science=90, Hindi=85}
Keys present in the hashmap : [Maths, English, Science, Hindi]
Now keySet() method is used to print the keys present in the hashmap. When the keySet() method is called it returns a set view of all the keys present in hte hashmap.
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