Aigle_Notes

Java - Arrays

Arrays are the ancestors of [[Java - Lists

ArrayList]].

Unlike ArrayList, we don’t have to import anything and create a separate object for it to work - arrays are natively supported in Java!

Creating an array

We can create an array by two ways - either we create it with the elements, or we specify the datatype and size to add them later.

String[] brands = {"espresso", "java", "latte"};

String[] brands = new String[2];

Referring from an array

The reference of an array is the information about the location of the data [i.e. its index].

When we use brands[1] to access the String java, we mean [go to the beginning of the array and then move forward 1 time. Then return a chunk of data the size of the variable.].

Using array index for operations

We can use array index to add, access, modify elements.

//adding elements
brands[0] = "espresso";
brands[1] = "java";

//modifying elements
brands[0] = "latte";

//accessing elements
System.out.println(array[0]);
System.out.println(array[1]);

Accessing the end of the list

Sometimes, we’d want to access the end of the list. We can already do this in ArrayList using IndexOf(), but now we want to do it with arrays.

If you use negative indices in array [like you would do in python], Java throws an ArrayIndexOutOfBoundsException error at you. This is because Java doesn’t support them in the first place.

• If it were supported, there may be problems such as a program reading the whole memory reserved for itself, index switching to max supported length if unchecked [see Integer Overflow], etc.

We use the workaround of using length [not a method call] to get the size of the array and subtracting 1 from it.

int lastIndex = brands.length - 1;

Variable size

Using an array

As parameter

You can use arrays as method parameters like this :

public static String printMenu(String[] brands)
{
//statements
}