Java Collections Framework

The Java Collections Framework provides a comprehensive set of classes and interfaces to manage groups of objects efficiently. It includes three main types of collections: List, Set, and Map.

Java Collections Framework provides various concrete implementations for List, Set, and Map. Some popular ones include:

Iterators allow traversing elements in a collection without exposing its internal structure. They provide a uniform way to access elements, regardless of the collection type.

Example of Using Iterator:

List<String> fruits = new ArrayList<>();
fruits.add(“Apple”);
fruits.add(“Banana”);
fruits.add(“Orange”);

Iterator<String> iterator = fruits.iterator();
while (iterator.hasNext()) {
String fruit = iterator.next();
System.out.println(fruit);
}

Java Collections Framework enables sorting elements based on custom criteria using Comparators. A Comparator defines the sorting order for elements in a collection.

Example of Sorting with Comparator:

class Employee {
private String name;
private int age;

// constructor and getters/setters
}

List<Employee> employees = new ArrayList<>();
// add employees to the list

Collections.sort(employees, Comparator.comparing(Employee::getName));