List in Java

In Java, a List is an ordered collection (also called a sequence) that allows duplicate elements. It is part of the Java Collections Framework and is defined in the java.util package.

🔑 Key Points about Lists

• They maintain insertion order.
• Can contain duplicate elements.
• Elements can be accessed via index (zero-based).
• Lists are dynamic in size (unlike arrays).

✅ Common Implementations of List

1. ArrayList
   • Backed by a dynamic array.Fast for random access.Slower for inserting/removing elements in the middle.
2. LinkedList
   • Implemented as a doubly linked list.Better for frequent insertions/deletions.Slower for random access.
3. Vector (Legacy)
   • Similar to ArrayList but synchronized (thread-safe).
   • Rarely used nowadays (use Collections.synchronizedList() instead).

🔧 Useful List Methods

List<String> list = new ArrayList<>();

list.add("A");           // Add element
list.add("B");
list.add("C");

list.get(1);             // Access element at index → "B"
list.set(1, "BB");       // Replace element at index 1
list.remove(0);          // Remove element at index 0
list.size();             // Get number of elements
list.contains("C");      // Check if element exists
list.isEmpty();          // Check if list is empty

for (String s : list) {  // Iteration
    System.out.println(s);
}

List<String> list = new ArrayList<>();

list.add("A");           // Add element
list.add("B");
list.add("C");

list.get(1);             // Access element at index → "B"
list.set(1, "BB");       // Replace element at index 1
list.remove(0);          // Remove element at index 0
list.size();             // Get number of elements
list.contains("C");      // Check if element exists
list.isEmpty();          // Check if list is empty

for (String s : list) {  // Iteration
    System.out.println(s);
}