Arrays In Java

  • An array is a list of similar things
  • An array has a fixed: name , type and length
  • These must be declared when the array is created.
  • Arrays sizes cannot be changed during the execution of the code

myArray has room for 8 elements.The elements are accessed by their index
in Java, array indices start at 0

Declaring Arrays :

int myArray[]:
declares myArray to be an array of integers
myArray = new int[8]:
sets up 8 integer-sized spaces in memory, labelled myArray[0] to myArray[7]
int myArray[] = new int[8]:
combines the two statements in one line.

Assigning Values:

refer to the array elements by index to store values in them.
myArray[0] = 3;
myArray[1] = 6;
myArray[2] = 3;   ...
can create and initialise in one step:
int myArray[] = {3, 6, 3, 1, 6, 3, 4, 1};

Iterating Through Arrays
for loops are useful when dealing with arrays:

for (int i = 0; i < myArray.length; i++) {
  myArray[i] = getsomevalue();

Arrays of Objects:
  • So far we have looked at an array of primitive types.
           -> integers
           -> could also use doubles, floats, characters…
  • Often want to have an array of objects
         Ex: Students, Books, Loans 
  • Need to follow 3 steps
Declaring the Array :
  1. Declare the array                                                                    private Student studentList[]; this declares studentList 
  2. Create the array                                                                              studentList = new Student[10];                                                        this sets up 10 spaces in memory that can hold references to Student objects
  3. Create Student objects and add them to the array:                          studentList[0] = new Student("Cathy", "Computing");
Sample Example:

class ArraysExample{
 public static void main(String[] args) {
  int[] ia = new int[101];
  for (int i = 0; i < ia.length; i++)
   ia[i] = i;
  int sum = 0;
  for (int i = 0; i < ia.length; i++)
   sum += ia[i];

Enter your email address to get our daily JOBS & INTERVIEW FAQ's Straight to your Inbox.

Make sure to activate your subscription by clicking on the activation link sent to your email