Last time we looked at comments. More importantly, the time before, we learnt about variables and that they can be used as a container to hold a value for the duration of the program
Today
Today we're going to learn what arrays are, what they're used for and how to use them
What's an array
An array is a variable which holds more than one value, it holds a list of values. For example, I could have an array containing the names of everyone in a school
An array can be an array of String, an array of ints, or an array of anything else
Why are they useful
They are used when we need to store lots of data of the same type. For example I might want to store a list of names, a list of places, countries, cars, basically anything
How to use them
Remeber an array can contain string, ints or anything else, but not a mixture. First we need to decide what our array is going to contain.
For this example, we'll be making an array of names containing Amy, Bob, Charlotte, Dave, Emma and Frank, so it will be Strings
Declare the array like so
String[] names = {"Amy", "Bob", "Charlotte", "Dave", "Emma", "Frank"};The String[] means this variable is going to be an array of strings
The array is called names
It contains the items wrapped in the curly braces, separated by commas
Accessing the values of an array
To print or modify the value of a certain item in an array we use it's index
The index of an item is it's position, counting from 0
So in this example, Amy has index 0, Bob's index is 1, Frank is 5 etc
To access a value we use the name of the array followed by the index is square brackets like so:
names[3]
So to print the name with index 3 we would use
System.out.println(names[3]);
This should print Dave
Similarly, we can change the value of an index by reassigning it
names[3] = "David"
Now when we do
System.out.println(names[3]);
We get David instead of Dave
For clarity here is the full code, commented
String[] names = { "Amy", "Bob", "Charlotte", "Dave", "Emma", "Frank" }; // This line defines the array
System.out.println(names[3]); // This should print Dave
names[3] = "David"; // This changes Dave to David
System.out.println(names[3]); // This should now print David
That's the end of this tutorial, next time we'll look at conditional statements
