Arrays are indexed sets of variables that store items in boxes like slots. Lists are sets of items where a missing item causes other items to shift, while in arrays a missing item leaves an empty slot. Arrays can be created using built-in functions and the Array Visualization object, which has properties and methods for manipulating array elements. Arrays represent collections of the same type of data, have a fixed size once created, and can be initialized using loops or shorthand notation.

1. Introduction to Data Structures

2. Arrays
An array is an indexed set of variables, such as
dancer[1], dancer[2], dancer[3],… It is like a set of
boxes that hold things.
A list is a set of items.
An array is a set of
variables that each
store an item.

3. Arrays and Lists
You can see the difference between arrays and
lists when you delete items.

4. Arrays and Lists
In a list, the missing spot is filled in when
something is deleted.

5. Arrays and Lists
In an array, an empty variable is left behind
when something is deleted.

6. Arrays
Arrays can be created in a similar manner, but
more often they are created using the array
visualization object from the Alice local gallery.
The Array Visualization object
has special properties and
methods for manipulating
the elements in an array.

7. Arrays
Alice has a set of built-in functions that can be
performed on arrays.

8. Introducing Arrays
Array is a data structure that represents a collection
of the same types of data.
myList[0]
myList[1]
myList[2]
myList[3]
myList[4]
myList[5]
myList[6]
myList[7]
myList[8]
myList[9]
double[] myList = new double[10];
myList reference
An Array of 10
Elements
of type double

9. Declaring Array Variables
• datatype[] arrayname;
Example:
double[] myList;
• datatype arrayname[];
Example:
double myList[];

10. Creating Arrays
arrayName = new datatype[arraySize];
Example:
myList = new double[10];
myList[0] references the first element in the
array.
myList[9] references the last element in the
array.

11. Declaring and Creating
in One Step
• datatype[] arrayname = new
datatype[arraySize];
double[] myList = new double[10];
• datatype arrayname[] = new
datatype[arraySize];
double myList[] = new double[10];

12. The Length of Arrays
• Once an array is created, its size is fixed. It
cannot be changed. You can find its size
using
arrayVariable.length
For example,
myList.length returns 10

13. Initializing Arrays
• Using a loop:
for (int i = 0; i < myList.length; i++)
myList[i] = i;
• Declaring, creating, initializing in one step:
double[] myList = {1.9, 2.9, 3.4, 3.5};
This shorthand syntax must be in one
statement.

14. Declaring, creating, initializing
Using the Shorthand Notation
double[] myList = {1.9, 2.9, 3.4, 3.5};
This shorthand notation is equivalent to the
following statements:
double[] myList = new double[4];
myList[0] = 1.9;
myList[1] = 2.9;
myList[2] = 3.4;
myList[3] = 3.5;