HASHMAP
Hey
guys, today we are back with another blog and we are going to talk about
Hashmaps in java in this one. So hope you’ll like this blog and do let us know
your reviews in the comments below.
We
have already learnt about arraylist
which can be used to store desired number of values inside it and hashmaps are also quite similar to arraylists
but unlike arraylists ,hashmaps can store values inside it with a key value,
i.e., hashmaps can store values of same or different types and the first value
can be the reference value or the key value for the second value. Now let’s see
the syntax of how to create a hashmap object in java and its implementation.
Firstly
we have to import the hashmaps class inside our code:
import java.util.HashMap;
After
importing our class we will create an hashmap object.
Syntax:
HashMap <Type, Type> objectName = new
HashMap<Type,Type>();
And
after creating an object we can use the put(), method to insert values
inside our Hashmap for each pair of values.
Ex:
import
java.util.HashMap;
public class
Coding_Winds {
public static void
main(String[] args) {
HashMap <String, Integer> marks = new
HashMap<>();
marks.put("Paul", 98);
marks.put("Alicia", 89);
marks.put("Morty", 85);
marks.put("Anna", 79);
System.out.println(marks);
}
}
Output: {Alicia=89, Morty=85, Paul=98, Anna=79}
Note
that, like arraylist in hashmaps also we have to write the full name of the
types (starting with the capital letter) of our pair values when we declare
them inside the angular brackets i.e., ‘Character’ for char types, ‘Double’ for
double, ‘Boolean’ for boolean, etc.
Now
like arraylists, hashmaps also have a lot of functions to manipulate a hashmap.
i) keyset() & values():
These two methods are used to access the key
value( or the first value) and the main value (or the second value) of a pair
respectively.
Ex:
import
java.util.HashMap;
public class
Coding_Winds {
public static void
main(String[] args) {
HashMap <String, Integer> marks = new
HashMap<>();
marks.put("Paul", 98);
marks.put("Alicia", 89);
marks.put("Morty", 85);
marks.put("Anna", 79);
System.out.println(marks.keySet());
System.out.println(marks.values());
}
}
Output: [Alicia, Morty, Paul, Anna]
[89, 85, 98, 79]
ii) get():
This
method simply gets us the main value if we pass the key value of any pair through
the get() method.
Ex:
import
java.util.HashMap;
public class
Coding_Winds {
public static void
main(String[] args) {
HashMap <String, Integer> marks = new
HashMap<>();
marks.put("Paul", 98);
marks.put("Alicia", 89);
marks.put("Morty", 85);
marks.put("Anna", 79);
System.out.println(marks.get("Paul"));
}
}
Output : 98
Some
of the other methods for hashmaps (remove(), size(), clear()) have exact
same functionalities as it is for an arraylist, but here both the values are
affected if any method is implemented.
Hope you are clear on this topic do read our more articles on JAVA LANGUAGE.
If you still have any doubt on this topic then do come to us via email "sophomoretechs@gmail.com" or via Instagram "@coding.winds".
This article is SUBMITTED By : Pranjal Rai
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