Updating a java map entry

Updating a java map entry

In Java, you can update a Map entry by using the put method to replace the existing value associated with a key. If the key already exists in the map, the put method will update the value associated with that key. Here's how you can update a map entry:

import java.util.HashMap;
import java.util.Map;

public class Main {
    public static void main(String[] args) {
        // Create a sample map
        Map<String, Integer> map = new HashMap<>();
        
        // Add some key-value pairs to the map
        map.put("apple", 10);
        map.put("banana", 5);
        map.put("cherry", 7);
        
        // Display the original map
        System.out.println("Original Map: " + map);
        
        // Update the value associated with the "banana" key
        map.put("banana", 8);
        
        // Display the updated map
        System.out.println("Updated Map: " + map);
    }
}

In this example:

  1. We create a HashMap named map and add some key-value pairs to it.

  2. To update the value associated with the "banana" key, we use the put method again with the same key but a new value ("8" in this case).

  3. The updated map is displayed to show that the value associated with the "banana" key has been successfully updated.

Keep in mind that if the key you are trying to update does not exist in the map, the put method will add a new key-value pair to the map. If you want to update a key only if it exists and do nothing if it doesn't exist, you can use the containsKey method to check for the key's existence before updating it.

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