How do you create a dictionary in Java?

To create a dictionary (or map) in Java, you can use the Map interface and its implementing classes.

The Map interface is a part of the java.util package and represents a key-value mapping. It has methods for inserting, deleting, and looking up values based on their keys.

There are several implementing classes of the Map interface, including HashMap, TreeMap, and LinkedHashMap. Each of these classes has its own characteristics and trade-offs, and you can choose the one that best fits your needs.

Here is an example of how to create a dictionary (HashMap) in Java:

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

public class Main {
  public static void main(String[] args) {
    Map<String, Integer> dictionary = new HashMap<>();
    dictionary.put("apple", 1);
    dictionary.put("banana", 2);
    dictionary.put("orange", 3);
  }
}

This code creates a HashMap with String keys and Integer values and adds three key-value pairs to it.

You can use the put() method to add key-value pairs to the map, the get() method to look up a value based on its key, and the remove() method to delete a key-value pair.

For example:

int value = dictionary.get("apple");  // Returns 1
dictionary.remove("apple");  // Removes the "apple" key-value pair

You can also use the containsKey() method to check if a key is present in the map and the size() method to get the number of key-value pairs in the map.

boolean hasApple = dictionary.containsKey("apple");  // Returns false
int size = dictionary.size();  // Returns 2

It is important to note that the Map interface and its implementing classes do not allow duplicate keys. If you try to insert a key-value pair with a key that is already present in the map, the value will be overwritten.