Using an Array in Java

Drawing Quick Response Code in Java Using an Array

zero-based arrays, such as Visual Basic and REALbasic One-based arrays are less common, but found in some versions of BASIC along with less popular languages like Pascal and Smalltalk When defining arrays, always make sure you know whether your programming language creates zero-based or one-based arrays Otherwise, you may try to store data in non-existent array elements

To avoid confusion, some programming languages (such as Pascal) let you define both the lower and upper bound arrays If you wanted to create an array to hold five integers, you could use the following code:

Var LotteryNumbers[15] of Integer;

This would number the LotteryNumbers array from 1 to 5 However, you could choose any number range of five like this:

Var LotteryNumbers[3337] of Integer;

This would create an array of five elements, numbered from 33 to 37, as shown in Figure 1-4

Var LotteryNumbers[3337] of Integer;

One advantage of defining the numbering of an array is that you can use meaningful numbers For example, if you wanted to store the names of employees in an array, you could number the array so each array element is identified by an employee number So if Jan Howards has employee ID number 102, Mike Edwards has employee ID number 103, and John

Perkins has employee ID number 104, you could create a three-element array, as shown in Figure 1-5, like this:

Var EmployeeList[102104] of String;

Var EmployeeList[102104] of String; Figure 1-5: By defining your own numbering for an array, you can make those numbers useful and meaningful 102 Jan Howards 103 Mike Edwards 104 John Perkins

When you define an array, it s a good idea to initialize that array Initializing an array means filling it with initial data, such as

Zeroes for storing numbers in an array Spaces for storing strings in an array If you don t initialize an array, the computer may randomly store data in an array, which could confuse your program later

To initialize an array, most programmers use a loop This code uses a FORNEXT loop to initialize an array with zeroes:

Dim LotteryNumbers(5) as Integer For I = 1 to 5 LotteryNumbers(I) = 0 Next I 1114 @Heading 4:Declarations

Some programming languages let you initialize an array without a loop Instead, you declare an array and its initial data on the same line This C++ code declares an array that can hold five integers and stores 0 in each array element:

int lotterynumbers[] = {0, 0, 0, 0, 0};

To store data in an array, you need to define two items: The array name The array element where you want to store the data So if you wanted to store data in the first element of a zero-based array, you could do this:

int myarray[5]; myarray[0] = 357;

If you wanted to store data in the first element of a one-based array, you could do this:

Dim myarray(5) as Integer myarray(1) = 357

You can store data in array elements in any order you want, such as storing the number 47 in the first array element, the number 91 in the fourth array element, and the number 6 in the second array element, such as

int myarray[5]; myarray[0] = 47; myarray[3] = 91; myarray[1] = 6;

To retrieve data from an array, you need to identify The array name The array element number that contains the data you want to retrieve Suppose you had the following BASIC code that creates an array that stores three names:

Dim Names(3) as String Names(1) = Nancy Titan Names(2) = Johnny Orlander Names(3) = Doug Slanders

If you wanted to retrieve and print the data stored in the second element of the Names array, you could use the following:

Print Names(2)