1 of 11

Arrays (Java/Turing)

CPT Girls

2 of 11

What are we covering?

When to Use Arrays

Let’s say you needed to create a program that would allow the user to input 15 names. Once all input has been received, it outputs all 15 names.
To do this, you could use 15 variables…
Or you could use an array!

What is an array

A list of values being stored
An index (number) is assigned to each value
Could be any data type
In Java and Turing, you may only store one type of data in a given array
Regular arrays hold a fixed number of objects (you must give the size of the array when creating it)

What is an array

Indices start at 0 in Java
Indices start at any integer you’d like (even negative!) in Turing
In Turing you can also have any keyboard character as indices (so instead of an index of 0 to 4 you could have ‘A’ to ‘F’)
Note though that the starting index must be smaller than the stoping index

What is an array

Example of Java/Turing number indexes

Example of Turing character indexes

Indices	0	1	2	3	4
Elements	“CPT!”	“is!”	“the!”	“coolest!”	“club!”

Indices	A	B	C	D	E
Elements	“CPT!”	“is!”	“the!”	“coolest!”	“club!”

Syntax

	Turing	Java
Initialization	var [arrayName]: array [start index] .. [stop index] of [data type]	int [] myArray = new int [5]
Assignment	my_array(0) := 17	myArray[0] = 17
Comparison	if my_array(0) = 17 then	if (myArray[0] == 17)

Index number

Helpful commands for arrays (Turing)

upper (arrayname) → returns the upper bound/stopping index of the array (for char arrays it will return the ASCII value of the char)
lower (arrayname) → returns the lower bound/starting index of the array (for char arrays it will return the ASCII value of the char)

Helpful commands for arrays (Java)

Extending - Parallel Arrays

Example problems