Sorted Map Interface Example in Java

Introduction

Sorted Map Interface is a classic Java console program that demonstrates the concept with complete source code and sample output. The Collections Framework provides ArrayList, HashMap, HashSet and related data structures.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

Sorted Map Interface defines a map that’s sorted by the keys provided. Using, once again, the compareTo() method or a method provided in the constructor to the sorted map, the key-element pairs are sorted by the keys. The first and last keys on the map can be called. Additionally, submaps can be created from the minimum and maximum keys. SortedMap is implemented by TreeMap.

Syntax

SortedMap<key-variable-type, value-variable-type> variable-name= new TreeMap<key-variable-type, value-variable-type>();

Example Program

import java.util.Map;
import java.util.SortedMap;
import java.util.TreeMap;

public class SortedMapInterfaceExample {

    public static void main(String[] args) {
        SortedMap<String, String> sortedMap = new TreeMap<String, String>();
        sortedMap.put("One", "NORTH");
        sortedMap.put("Two", "SOUTH");
        sortedMap.put("Three", "EAST");
        sortedMap.put("Four", "WEST");
        for (Map.Entry map : sortedMap.entrySet()) {
            System.out.println("Key is : " + map.getKey() + " and Value is : " + map.getValue());
        }
    }
}

Sample Output

Key is : Four and Value is : WEST
Key is : One and Value is : NORTH
Key is : Three and Value is : EAST
Key is : Two and Value is : SOUTH

When to use

Use this sorted map interface example when learning or revising core Java syntax.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.util.Map; imports a class used later in the program.

3. import java.util.SortedMap; imports a class used later in the program.

4. import java.util.TreeMap; imports a class used later in the program.

5. SortedMap<String, String> sortedMap = new TreeMap<String, String>(); updates a variable used in the calculation or output.

6. A println / print call writes text to the console — part of the sample output below.

7. Compare your console output with the sample output for Sorted Map Interface to confirm the program behaves correctly.

Best Practices

Common Mistakes