Programming Basics: Loops and Arrays

Repetition Statements

• A loop structure repeatedly executes a block of code "as long as" a tested expression is true.
• If a loop's tested Boolean expression is true, a block of statements called the loop body executes. This occurs before the Boolean Expression is evaluated again.

Arrays

• An array is a container object holding a fixed number of values of the same type.
• Array length is set when the array is created.
• Each array item (element) is accessed by a numerical index.
• Arrays are declared using [ ] after the data type.
• Array instantiation uses the new keyword and specifies the array's dimensions.
• Array initialization assigns values to the elements. This can be done during instantiation or by assigning values by their indices.
• Looping through arrays can use the for loop or the for-each loop.

Two-Dimensional Arrays

• A multidimensional array holds one or more arrays.
• Creating a two-dimensional array involves placing each array within its curly braces.
• Accessing elements in a two-dimensional array requires specifying two indices: one for the array and one for the element within that array.
• Looping through a two-dimensional array requires nested for loops, one for each dimension.

ArrayList

• ArrayList is a dynamic array, meaning it can grow as needed.
• It is easier to manipulate than a traditional array (e.g., removing elements).
• It can only hold objects, not primitive data types.
• The java.util package contains the ArrayList class.
• There are several constructors for ArrayList to create an empty list, initialize it with a collection or set an initial capacity.
• Common methods for ArrayList include:
  • add(Object o): Adds an element to the end of the list.
  • remove(int index): Removes an element at a specific index.
  • set(int index, Object o): Replaces the element at a specific index with another element.
  • contains(Object o): Checks if the list contains a specific element.
  • indexOf(Object o): Returns the index of the first occurrence of a specific element.
  • get(int index): Retrieves the element at a specific index.
  • clear(): Removes all elements from the list.
  • size(): Returns the number of elements in the list.

ArrayList vs. Array

• Arrays have a fixed size, while ArrayList can grow dynamically.
• ArrayList offers more functionalities than arrays, like removing elements, easily finding elements, resizing, etc.

Using ArrayList

• Importing the ArrayList class is needed for using it.
• Creating an ArrayList is done using the syntax: ArrayList list = new ArrayList();
• Adding elements to an ArrayList is done using the add() method.
• Retrieving an element from an ArrayList is done using the get(index) method.
• Modifying an existing element in an ArrayList is done using the set(index, value) method.
• Determining the size of an ArrayList is done using the size() method.
• Looping through elements in an ArrayList can be done with a for loop, a for-each loop, or an iterator (not discussed in the text).

Explore the fundamentals of loops and arrays in programming. This quiz covers repetition statements, how to declare and initialize arrays, and the concept of two-dimensional arrays. Test your understanding of these essential programming concepts.