Exercise $2$: Java Wildcards

In a new program write a method printList that takes a List of any type and prints each element in the list. Use wildcards to achieve this.

Hints:

$$ Wildcards: Use wildcards $(?)$ to write more flexible code that can work with any subtype of a given class. Remember, $?$ extends T is bounded wildcard for subtypes of T$,$ and $?$ super T is for supertypes of T$.$

$$ Use Case for Wildcards: Use wildcards when you need to process data from a collection but don't need to add new data to the collection or when the operation is read$-$only.

$$ Upper Bounded Wildcard Example: If you have a method that needs to read a list of numbers and calculate their sum, use List as the method parameter. This allows the method to work with a list of Integer, Double, or any other type that extends Number.

$$ Lower Bounded Wildcard Example: If you have a method that needs to add integers to a list, use List as the method parameter. This ensures that you can pass a list of Integer or a list of any superclass of Integer $($like Number or Object$).$

$$ Avoid Wildcards for Return Types: Generally, avoid using wildcards in return types because they can make the method's return type more difficult to work with. Instead, use specific types or generic type parameters.

Exercise $3$: Java ArrayList

In a new program, create an ArrayList of $8$ strings. After creating the ArrayList, do the following:

$$ add $2$ elements to it

$$ modify an element

$$ print all elements

$$ remove an element by index

$$ remove an element by string value

$$ ArrayList: Utilize add$(),$ get$(),$ set$(),$ remove$(),$ and size$()$ methods for managing elements.

$$ Importing ArrayList: Ensure you import the java.util.ArrayList package at the beginning of your Java program.

$$ Looping Through an ArrayList: You can use a standard for loop, an enhanced for loop, or an iterator to loop through an ArrayList. When using a standard for loop, use the size$()$ method for setting the loop's condition.