If you are a Java developer, you must have come across the concept of Map, which is a key-value based data structure. While using Map, you might have faced a situation where you need to store multiple values for a single key. In such scenarios, you can use a List as the value for a key in the Map. This article will explain how to implement a Map with List as value in Java.
Table of Contents
Table of Contents
Introduction
If you are a Java developer, you must have come across the concept of Map, which is a key-value based data structure. While using Map, you might have faced a situation where you need to store multiple values for a single key. In such scenarios, you can use a List as the value for a key in the Map. This article will explain how to implement a Map with List as value in Java.
Creating a Map with List as value
The first step is to create a Map object. In this case, we will be using the HashMap implementation of the Map interface. Then, we will create a List to store the values for each key. Finally, we will add the key-value pair to the Map, where the value is a List.
Here's the code:
```java MapRetrieving the values from the Map
Once you have added the key-value pair to the Map, you can retrieve the values using the get() method. The get() method returns the List for a given key. You can then iterate over the List to retrieve the values.
Here's the code:
```java ListAdding values to the List
To add values to the List, you can retrieve the List for a given key using the get() method, and then use the add() method to add the value to the List.
Here's the code:
```java ListRemoving values from the List
To remove a value from the List, you can retrieve the List for a given key using the get() method, and then use the remove() method to remove the value from the List.
Here's the code:
```java ListIterating over the Map
You can iterate over the Map using a for-each loop. The loop will iterate over the key-value pairs in the Map, where the value is a List.
Here's the code:
```java for(Map.EntryQuestion & Answer
Q. What is a Map in Java?
A. A Map is a key-value based data structure in Java.
Q. How can you store multiple values for a key in a Map?
A. You can use a List as the value for a key in the Map.
Q. How can you retrieve the values for a key in a Map with List as value?
A. You can retrieve the List for a given key using the get() method, and then iterate over the List to retrieve the values.
Q. How can you add values to a List in a Map with List as value?
A. You can retrieve the List for a given key using the get() method, and then use the add() method to add the value to the List.
Q. How can you remove a value from a List in a Map with List as value?
A. You can retrieve the List for a given key using the get() method, and then use the remove() method to remove the value from the List.