LinkedHashMap and TreeMap for Sorted Key-Value Pairs

Intermediate13 min read•Updated: 2026-10-22

🌲 LinkedHashMap and TreeMap for Ordered Key-Value Pairs

Introduction

While HashMap provides maximum speed with no ordering, enterprise scenarios often require preserving insertion order or maintaining keys in strict sorted order.

📊 Comparison

Map Type	Key Ordering	Complexity	Best Use Case
`HashMap`	Arbitrary	O(1) Average	General dictionaries, caches
`LinkedHashMap`	Insertion Order	O(1)	LRU Caches, predictable iteration
`TreeMap`	Sorted Key Order	O(log N)	Range queries, alphabetical indexes

1import java.util.Map;
2import java.util.TreeMap;
3 
4public class TreeMapDemo {
5    public static void main(String[] args) {
6        Map<String, Integer> studentRolls = new TreeMap<>();
7        studentRolls.put("Vikram", 105);
8        studentRolls.put("Aarav", 101);
9        studentRolls.put("Pooja", 103);
10 
11        // Traverses in strictly sorted alphabetical order of keys:
12        studentRolls.forEach((name, roll) -> {
13            System.out.printf("%s -> Roll #%d%n", name, roll);
14        });
15    }
16}

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File Streams: FileReader, FileWriter, BufferedReader, and BufferedWriter

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Map Interface: HashMap Internal Working (Buckets, Hash Codes, Collisions)	File Streams: FileReader, FileWriter, BufferedReader, and BufferedWriter

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File Streams: FileReader, FileWriter, BufferedReader, and BufferedWriter

LinkedHashMap and TreeMap for Sorted Key-Value Pairs

Intermediate13 min read•Updated: 2026-10-22

Study Materials

🌲 LinkedHashMap and TreeMap for Ordered Key-Value Pairs

Introduction

While HashMap provides maximum speed with no ordering, enterprise scenarios often require preserving insertion order or maintaining keys in strict sorted order.

📊 Comparison

Map Type	Key Ordering	Complexity	Best Use Case
`HashMap`	Arbitrary	O(1) Average	General dictionaries, caches
`LinkedHashMap`	Insertion Order	O(1)	LRU Caches, predictable iteration
`TreeMap`	Sorted Key Order	O(log N)	Range queries, alphabetical indexes

1import java.util.Map;
2import java.util.TreeMap;
3 
4public class TreeMapDemo {
5    public static void main(String[] args) {
6        Map<String, Integer> studentRolls = new TreeMap<>();
7        studentRolls.put("Vikram", 105);
8        studentRolls.put("Aarav", 101);
9        studentRolls.put("Pooja", 103);
10 
11        // Traverses in strictly sorted alphabetical order of keys:
12        studentRolls.forEach((name, roll) -> {
13            System.out.printf("%s -> Roll #%d%n", name, roll);
14        });
15    }
16}

Next Lesson

File Streams: FileReader, FileWriter, BufferedReader, and BufferedWriter

Continue learning with hands-on practice, examples, and exercises in the upcoming topic.

Related Lessons

Previous Lesson	Next Lesson
Map Interface: HashMap Internal Working (Buckets, Hash Codes, Collisions)	File Streams: FileReader, FileWriter, BufferedReader, and BufferedWriter

Practice Quiz

Test your understanding of this lesson with 1 questions. Each question has one correct answer.

Previous Next