Arrays

1
Arrays

• Lists, matrices and more

2
Arrays

• Arrays are objects, like Strings
• You must declare, create and initialize
• Ex char row
• row new char5
• row0 'A'
• row1 'B'
• row2 'C'
• row3 'D'
• row4 'E'

3
Arrays

• Or you can declare, create and initialise in one
  line
• Ex char row 'A', 'B', 'C', 'D', 'E'
• Note the Java compiler will initialize an array
  for you in case you forget, bad habit!
• ints and doubles will have the value 0
• booleans the value false
• chars the value ''
• Strings and other object the value null

4

• If you try to print it, this is what happens
• System.out.println("Here is the row " row)
• You cannot print it because row is only a memory
  address!!!

5

• Here how it works
• By doing row new char you only get an
  address in the computers memory
• To access the elements of the row, you must
  specify which one using the and an index Ex
  row1
• The index starts at 0
• instead if you try
• System.out.println("Here is 1st element "
  row0)
• then you would get

6
Result
7
Looping with Arrays

• To access all the elements, you can use a loop!
• Ex
• for (i 0 i lt 5 i)
• System.out.println("Here is the " i "
  element " rowi)

8
Result
9
Assignment 3

• Write a program that uses an array containing all
  the months of the year. Using a for loop,
  display all the months on the console
• Hint you want to create an array of Strings,
  which are also objects

10
Expected result