Java Code Example: simple TreeMap example

import java.util.TreeMap;

public class TreeMapExample {
    public static void main(String[] args) {
        // create a TreeMap
        TreeMap<String, Integer> treeMap = new TreeMap<>();

        // put some key-value pairs in the map
        treeMap.put("Alice", 25);
        treeMap.put("Bob", 30);
        treeMap.put("Charlie", 35);

        // print the TreeMap
        System.out.println("TreeMap: " + treeMap);

        // get the value associated with a key
        int bobAge = treeMap.get("Bob");
        System.out.println("Bob's age: " + bobAge);

        // remove a key-value pair from the map
        System.out.println("TreeMap after removing Charlie: " + treeMap);

        // get the size of the map
        int size = treeMap.size();
        System.out.println("Size of the TreeMap: " + size);

        // get the first and last keys in the map
        String firstKey = treeMap.firstKey();
        String lastKey = treeMap.lastKey();
        System.out.println("First key: " + firstKey);
        System.out.println("Last key: " + lastKey);

This code creates a TreeMap called treeMap, which maps String keys to Integer values. We then add some key-value pairs to the map using the put() method.

We then print the entire TreeMap using the println() method.

We retrieve the value associated with the key "Bob" using the get() method, and print it.

We then remove the key-value pair associated with the key "Charlie" using the remove() method.

We use the size() method to determine the number of key-value pairs in the map, and print it.

Finally, we use the firstKey() and lastKey() methods to retrieve the first and last keys in the map, respectively, and print them.

The output of this code will be:

TreeMap: {Alice=25, Bob=30, Charlie=35}
Bob's age: 30
TreeMap after removing Charlie: {Alice=25, Bob=30}
Size of the TreeMap: 2
First key: Alice
Last key: Bob

This example demonstrates some of the basic operations that can be performed using a TreeMap.