The IdentityHashMap.values()
method in Java returns a collection view of the values contained in the map. This guide will cover the method’s usage, explain how it works, and provide examples to demonstrate its functionality. We will also cover a real-world use case to show how IdentityHashMap.values()
can be used effectively.
Table of Contents
- Introduction
values
Method Syntax- Examples
- Basic Usage of
values
Method - Iterating Over Values
- Basic Usage of
- Real-World Use Case
- Example: Displaying User Session Statuses
- Conclusion
Introduction
The IdentityHashMap.values()
method is a member of the IdentityHashMap
class in Java. This class uses reference equality (==) instead of object equality (equals()) when comparing keys. The values
method returns a collection view of the values contained in the map.
values() Method Syntax
The syntax for the values
method is as follows:
public Collection<V> values()
- Parameters: This method does not take any parameters.
- Returns: A collection view of the values contained in this map.
Examples
Basic Usage of values
Method
The values
method can be used to get a collection view of the values contained in the IdentityHashMap
.
Example
import java.util.IdentityHashMap;
import java.util.Collection;
public class IdentityHashMapValuesExample {
public static void main(String[] args) {
// Creating an IdentityHashMap
IdentityHashMap<String, Integer> map = new IdentityHashMap<>();
// Adding key-value pairs to the IdentityHashMap
map.put("Ravi", 25);
map.put("Priya", 30);
map.put("Vijay", 35);
// Getting the collection view of the values
Collection<Integer> values = map.values();
// Printing the collection view of the values
System.out.println("IdentityHashMap Values: " + values);
}
}
Output:
IdentityHashMap Values: [25, 30, 35]
Iterating Over Values
You can iterate over the values in the IdentityHashMap
using the collection view returned by the values
method.
Example
import java.util.IdentityHashMap;
import java.util.Collection;
public class IdentityHashMapIterateValuesExample {
public static void main(String[] args) {
// Creating an IdentityHashMap
IdentityHashMap<String, Integer> map = new IdentityHashMap<>();
// Adding key-value pairs to the IdentityHashMap
map.put("Ravi", 25);
map.put("Priya", 30);
map.put("Vijay", 35);
// Getting the collection view of the values
Collection<Integer> values = map.values();
// Iterating over the values
for (Integer value : values) {
System.out.println("Value: " + value);
}
}
}
Output:
Value: 25
Value: 30
Value: 35
Real-World Use Case
Example: Displaying User Session Statuses
A common real-world use case for IdentityHashMap.values()
is displaying the statuses of user sessions in a web application where reference equality is required.
Example
import java.util.IdentityHashMap;
import java.util.Collection;
public class UserSessionStatusDisplay {
static class UserSession {
private String sessionId;
private String userName;
public UserSession(String sessionId, String userName) {
this.sessionId = sessionId;
this.userName = userName;
}
@Override
public String toString() {
return "UserSession{" +
"sessionId='" + sessionId + '\'' +
", userName='" + userName + '\'' +
'}';
}
}
public static void main(String[] args) {
// Creating user sessions
UserSession session1 = new UserSession("S1", "Ravi");
UserSession session2 = new UserSession("S2", "Priya");
UserSession session3 = new UserSession("S3", "Vijay");
// Creating an IdentityHashMap to manage user sessions
IdentityHashMap<UserSession, String> sessionMap = new IdentityHashMap<>();
sessionMap.put(session1, "Active");
sessionMap.put(session2, "Inactive");
sessionMap.put(session3, "Active");
// Getting the collection view of the values (statuses)
Collection<String> statuses = sessionMap.values();
// Displaying the user session statuses
for (String status : statuses) {
System.out.println("Session Status: " + status);
}
}
}
Output:
Session Status: Active
Session Status: Inactive
Session Status: Active
In this example, IdentityHashMap.values()
is used to display the statuses of user sessions, where sessions are identified by reference equality, making it suitable for scenarios where unique object references are crucial.
Conclusion
The IdentityHashMap.values()
method in Java provides a way to get a collection view of the values contained in the map, using reference equality for key comparison. By understanding how to use this method, you can efficiently manage collections of key-value pairs where reference equality is required. This method allows you to utilize the power of IdentityHashMap
for various scenarios, making it a versatile tool for managing collections of key-value pairs based on reference equality.