Example of Multimap framework in Java Class Library Collections
Example of Multimap framework in Java Class Library Collections
Introduction:
In Java development, Multimap is an important component in the Java collection framework.It provides a convenient way to handle the collection of key-value, especially when a key can correspond to multiple values.This article will introduce the basic concepts of Multimap, and how to use the Multimap framework in the Java class library Collections for common operations.
Multimap Overview:
Multimap is an extension of the concept of one -mapping data structure, which allows one key (key) to correspond to multiple values (values).This is very useful in many scenarios. For example, a student can take multiple courses, and one animal can have multiple segmented classifications.
The Java class library Collections provides Multimap interfaces and several implementation classes, including: Listmultimap, Setmultimap, and SortedSetmultimap.These implementation classes provide different types of value sets and have their own characteristics, which can be selected and used according to specific needs.
Example:
Below we will demonstrate how to use the Multimap framework through a simple example.
import com.google.common.collect.ArrayListMultimap;
import com.google.common.collect.Multimap;
public class MultimapExample {
public static void main(String[] args) {
Multimap<String, String> multimap = ArrayListMultimap.create();
// Add key value pairs to Multimap
multimap.put ("Chinese", "Zhang San");
multimap.put ("Chinese", "Li Si");
multimap.put ("Mathematics", "Wang Wu");
multimap.put ("English", "Zhao Liu");
multimap.put ("English", "Qianqi");
// Get all the value corresponding to the key
System.out.println ("Language Delivery Student: + Multimap.get (" Language ");
// Remove the specified key value pair
multimap.remove ("Mathematics", "Wang Wu");
System.out.println ("Mathematical Objective Student: + Multimap.get (" Mathematics ");
// Get all the keys in Multimap
System.out.println ("All subjects:" + Multimap.keys ());
// Clear multimap
multimap.clear();
System.out.println ("Multimap has been empty:" + multimap.isempty ());
}
}
In the above example, we use the ArrayListMultimap implementation class provided by the Google Guava library to create a Multimap object.Then, we add key value pairs to the Multimap through the `Put` method, obtain all values corresponding to the specified key through the` Get` method, and remove the specified key value pair through the `Remove` method.Finally, we use the `Keys` method to get all the keys in Multimap, and use the` clear` method to empty Multimap.
in conclusion:
The Multimap framework in the Java Class Library Collection provides a convenient way to handle more mapping relationships.Whether the key can correspond to multiple values, it is necessary to store more demand for one -mapping relationship. Multimap is a powerful and practical tool.Through the example and introduction of this article, readers can quickly use the Multimap framework in the Java class library Collections.
