CommonMethodsDemo.java

package Collections.Practice;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class CommonMethodsDemo {
    public static void main(String[] args) {

        System.out.println("=== COLLECTION COMMON METHODS DEMO ===\n");

        /*
         IMPORTANT CONCEPT:
         We are using the Collection interface as the reference type.
         The object type is ArrayList.
        */

        Collection<String> fruits = new ArrayList<>();

        // ------------------------------
        // add()
        // ------------------------------

        System.out.println("Adding elements using add()");

        fruits.add("Apple");
        fruits.add("Banana");
        fruits.add("Orange");
        fruits.add("Mango");

        System.out.println("Fruits: " + fruits);


        // ------------------------------
        // size()
        // ------------------------------

        System.out.println("\nChecking size of collection");

        int size = fruits.size();
        System.out.println("Size: " + size);


        // ------------------------------
        // contains()
        // ------------------------------

        System.out.println("\nChecking if collection contains certain items");

        boolean hasApple = fruits.contains("Apple");
        boolean hasGrape = fruits.contains("Grape");

        System.out.println("Contains Apple? " + hasApple);
        System.out.println("Contains Grape? " + hasGrape);


        // ------------------------------
        // remove()
        // ------------------------------

        System.out.println("\nRemoving an element");

        fruits.remove("Banana");

        System.out.println("After removing Banana:");
        System.out.println(fruits);


        // ------------------------------
        // addAll()
        // ------------------------------

        System.out.println("\nAdding multiple elements using addAll()");

        List<String> moreFruits = new ArrayList<>();
        moreFruits.add("Pineapple");
        moreFruits.add("Strawberry");
        moreFruits.add("Peach");

        fruits.addAll(moreFruits);

        System.out.println("After addAll:");
        System.out.println(fruits);


        // ------------------------------
        // Iterating through Collection
        // ------------------------------

        System.out.println("\nLooping through collection:");

        for (String fruit : fruits) {
            System.out.println(fruit);
        }


        // ------------------------------
        // isEmpty()
        // ------------------------------

        System.out.println("\nChecking if collection is empty");

        boolean empty = fruits.isEmpty();
        System.out.println("Is empty? " + empty);


        // ------------------------------
        // clear()
        // ------------------------------

        System.out.println("\nClearing the collection");

        fruits.clear();

        System.out.println("After clear:");
        System.out.println(fruits);


        System.out.println("\nCheck if empty after clear:");

        System.out.println("Is empty? " + fruits.isEmpty());


        // ------------------------------
        // TODO Exploration Section
        // ------------------------------

        /*
         TODO 1:
         Create a new Collection called numbers
         Add the following values:
         10, 20, 30, 40, 50
        */
Collections<Integer> numbers = new ArrayList<>();
        numbers.add(10);
        numbers.add(20);
        numbers.add(30);
        numbers.add(40);
        numbers.add(50);

      //  num.addAll(numbers);


        /*
         TODO 2:
         Print the size of the numbers collection
        */

        System.out.println(numbers.size());
        /*
         TODO 3:
         Check if the collection contains 30
        */
boolean hasNum= numbers.contains(30);

        /*
         TODO 4:
         Remove the number 20
        */
int newNum = numbers.remove(20);

        /*
         TODO 5:
         Loop through the numbers collection
         and print each value
        */

for(int n:numbers){
    System.out.println(n);
}
        /*
         REFLECTION QUESTIONS:

         1. Why can we use Collection as the reference type?
         Because ArrayList implements the Collection interface.
         ArrayList is a class that implements List, and List extends Collection.
So an ArrayList is a type of Collection, which allows us to store it in a Collection reference.

         2. What methods are available because of the Collection interface?
         add()
         remove()
         contains()
         size()
         isEmpty()
         clear()
         iterator()
         3. What methods are NOT available when using Collection instead of List?
         Methods that belong only to List are not available when the reference type is Collection.
Examples of List-only methods:
get(index)
set(index, element)
add(index, element)
remove(index)
indexOf()
         */
    }

}