1. Java Array
ISYS 350

2. Array
An array allows you to store a group of items of the same type together.
Processing a large number of items in an array is easier than processing a large number of items stored in separate variables.

3. Declaring a Array Examples of declaring an array:
int[] anArray = new int[10];
10 elements index from 0 to 9
double[] anArrayOfDoubles = new double[10];
String[] anArrayOfStrings = new String[10];
int[] anArray = { 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000};

4. Array Elements Array elements are indexed from 0 to array size – 1.
Each element can be accessed by its index:
arrayName[index]
Ex:
empName[0]
intRate[2]

5. Array Initialization With the declaration statement:
String[] empName = { "Peter", "Paul", "Mary" };
double[] intRate = { .03, .04, .05, .06, .07, .08 };
Initialize each element separately:
empName[0] = "Peter";
empName[1] = "Paul";
empName[2] = "Mary";

6. Accessing Array Elements with a for loop
Using array’s length property:
for (arrayIndex = 0; arrayIndex <= empName.length-1; ++arrayIndex) {
out.print(empName[arrayIndex]); }
Note: length - 1

7. Example: Compute the sum and average of numbers in an array
<%
String[] stName = { "Peter", "Paul", "Mary", "Nancy", "Linda"};
double[] myGPAs = { 2.5, 3.2, 3.4, 2.9, 3.6 };
for (int arrayIndex = 0; arrayIndex <= stName.length-1; ++arrayIndex) {
out.print(stName[arrayIndex] + ": GPA= " + myGPAs[arrayIndex]);
out.print("<br>"); }
double sumGPA=0, avgGPA;
for (int i = 0; i <= myGPAs.length - 1; ++i)
sumGPA += myGPAs[i];
avgGPA = sumGPA / myGPAs.length;
out.print("Average GPA is: " + avgGPA);
%>