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Java ArrayList

ArrayList is a resizable array implementation of the List interface in Java. It is part of the java.util package and provides dynamic arrays that can grow as needed.

1. Creating an ArrayList

import java.util.ArrayList;

public class ArrayListExample {
    public static void main(String[] args) {
        ArrayList<String> list = new ArrayList<>();
    }
}

2. Adding Elements

Use the add() method to add elements to the ArrayList.

list.add("Apple");
list.add("Banana");
list.add("Cherry");

3. Accessing Elements

Use the get() method to access elements by index.

String fruit = list.get(0); // Gets the first element
System.out.println(fruit); // Outputs: Apple

4. Iterating Over an ArrayList

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

5. Common Methods

  • size() - Returns the number of elements.
  • remove(int index) - Removes the element at the specified index.
  • clear() - Removes all elements.
  • contains(Object o) - Checks if the list contains the specified element.

6. Key Takeaways

  • ArrayList provides dynamic arrays in Java.
  • It's part of the java.util package and implements the List interface.
  • Allows duplicate elements and maintains insertion order.
  • Not synchronized; use Vector or synchronize externally if thread safety is required.
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