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Lesson 37

ArrayList and LinkedList

ArrayList for fast access. LinkedList for fast insert and delete.

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Lesson content

Both implement List. ArrayList uses array. LinkedList uses nodes.

Key Terms

  • ArrayList: Dynamic array. Fast index access.
  • LinkedList: Doubly linked nodes. Fast insert/delete.
  • List Interface: Ordered, allows duplicates.
  • Dynamic Size: Grows and shrinks automatically.

Example: ArrayList

import java.util.ArrayList;

public class ArrayListExample {
    public static void main(String[] args) {
        ArrayList<String> fruits = new ArrayList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Mango");
        System.out.println(fruits);
        System.out.println("First Fruit: " + fruits.get(0));
    }
}
[Apple, Banana, Mango]
First Fruit: Apple

Example: LinkedList

import java.util.LinkedList;

public class LinkedListExample {
    public static void main(String[] args) {
        LinkedList<String> fruits = new LinkedList<>();
        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Mango");
        System.out.println(fruits);
        System.out.println("First Fruit: " + fruits.get(0));
    }
}
[Apple, Banana, Mango]
First Fruit: Apple

Common Operations

list.add("Java");       // add
list.get(0);            // access
list.set(0, "Python");  // update
list.remove(0);         // remove
list.size();            // size

Iterating

for (String item : list) {
    System.out.println(item);
}

When to Use Each

  • ArrayList: Frequent reads, index access.
  • LinkedList: Frequent inserts and deletes.
  • LinkedList: Queue or deque operations.

FAQ

1. Main difference?

ArrayList — fast access. LinkedList — fast insert/delete.

2. Which is faster?

ArrayList for reads. LinkedList for modifications.

3. When LinkedList over ArrayList?

Frequent insert/delete at middle or beginning.

ArrayList — dynamic array, fast index access.
LinkedList — nodes with links, fast modifications.
Both allow duplicates and maintain order.
ArrayList uses less memory.
LinkedList faster at insert and delete.
Use ArrayList by default.
Program to List interface, not implementation.

Where Java is used

Java in real-world development

ArrayList

Dynamic array. Fast get(). Slower middle insert/delete.

LinkedList

Doubly linked nodes. Fast insert/delete. Slower random access.

Memory

ArrayList uses less. LinkedList stores prev/next references.

Use ArrayList When

More reads than writes. Index access needed.

Use LinkedList When

Frequent insert/delete. Queue or deque needed.

Best Practice

List<String> names = new ArrayList<>() — program to interface.

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