Collections Framework & Low-Level Data Structures

package com.accenture.ltt.collections;

import java.util.Comparator;

/**
 * Comparable vs Comparator:
 * - Comparable defines the NATURAL sorting order inside the class itself (compareTo).
 * - Comparator defines EXTERNAL custom sorting strategies without modifying the class.
 */
public class SortByNameComparator implements Comparator<Course> {
    @Override
    public int compare(Course c1, Course c2) {
        return c1.getCourseName().compareToIgnoreCase(c2.getCourseName());
    }
}

package com.accenture.ltt.collection.assignment.comparable;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

// Class implements Comparable to define its NATURAL order
class Course implements Comparable<Course> {
    private int courseId;
    private String courseName;
    private int courseFee;

    public Course(int id, String name, int fee) {
        this.courseId = id;
        this.courseName = name;
        this.courseFee = fee;
    }

    public int getCourseFee() { return courseFee; }
    public String getCourseName() { return courseName; }

    // compareTo defines sorting by course fee ascending
    @Override
    public int compareTo(Course o) {
        return Integer.compare(this.courseFee, o.courseFee);
    }
}

public class CourseComparableTester {
    public static void main(String[] args) {
        List<Course> courses = new ArrayList<>();
        courses.add(new Course(1056, "C#.Net", 20000));
        courses.add(new Course(1045, "Java", 15000));
        courses.add(new Course(4532, "Python", 20500));

        Collections.sort(courses); // Sorts automatically using compareTo()
        courses.forEach(c -> System.out.println(c.getCourseName() + " : $" + c.getCourseFee()));
    }
}

package com.accenture.ltt.collection.demo.map;

import java.util.*;

public class HashMapIteratorExample {
    public static void main(String[] args) {
        Map<Integer, String> directory = new HashMap<>();
        directory.put(404232, "Venkat Rajaram");
        directory.put(502113, "Tia Mathew");
        directory.put(562190, "Ali Mohammed");

        // Method 1: Iterating over keySet (Requires secondary map.get(key) lookup)
        for (Integer contact : directory.keySet()) {
            System.out.println("KeySet -> Contact: " + contact + " | Name: " + directory.get(contact));
        }

        // Method 2: Iterating over entrySet (MOST EFFICIENT: No secondary lookup!)
        for (Map.Entry<Integer, String> entry : directory.entrySet()) {
            System.out.println("EntrySet -> " + entry.getKey() + " = " + entry.getValue());
        }

        // Method 3: Java 8+ forEach BiConsumer lambda
        directory.forEach((k, v) -> System.out.println("Lambda -> " + k + " : " + v));
    }
}