Hello Friends Now I am going to learn that how we use Arrays in Java.Java provides a data structure, the array, which stores a
fixed-size sequential collection of elements of the same type. An array
is used to store a collection of data, but it is often more useful to
think of an array as a collection of variables of the same type.Instead of declaring individual variables, such as number0, number1,
..., and number99, you declare one array variable such as numbers and
use numbers[0], numbers[1], and ..., numbers[99] to represent individual
variables.This tutorial introduces how to declare array variables, create arrays, and process arrays using indexed variables.
Declaring Array Variables:
To use an array in a program, you must declare a variable to reference
the array, and you must specify the type of array the variable can
reference. Here is the syntax for declaring an array variable:
Example:
double[] myList; // preferred way.
or
double myList[]; // works but not preferred way.
Creating Arrays:
You can create an array by using the new operator with the following syntax:
arrayRefVar = new dataType[arraySize];
The above statement does two things:
- It creates an array using new dataType[arraySize];
- It assigns the reference of the newly created array to the variable arrayRefVar.
Declaring an array variable, creating an array, and assigning the
reference of the array to the variable can be combined in one statement,
as shown below:
dataType[] arrayRefVar = new dataType[arraySize];
Alternatively you can create arrays as follows:
dataType[] arrayRefVar = {value0, value1, ..., valuek};
The array elements are accessed through the index. Array indices are 0-based; that is, they start from 0 to arrayRefVar.length-1.
Example:
Following statement declares an array variable, myList, creates an array
of 10 elements of double type and assigns its reference to myList:
double[] myList = new double[10];
Following picture represents array myList. Here, myList holds ten double values and the indices are from 0 to 9.
Processing Arrays:
When processing array elements, we often use either for loop or
foreach loop because all of the elements in an array are of the same
type and the size of the array is known.
Example:
Here is a complete example of showing how to create, initialize and process arrays:
public class TestArray {
public static void main(String[] args) {
double[] myList = {1.9, 2.9, 3.4, 3.5};
// Print all the array elements
for (int i = 0; i < myList.length; i++) {
System.out.println(myList[i] + " ");
}
// Summing all elements
double total = 0;
for (int i = 0; i < myList.length; i++) {
total += myList[i];
}
System.out.println("Total is " + total);
// Finding the largest element
double max = myList[0];
for (int i = 1; i < myList.length; i++) {
if (myList[i] > max) max = myList[i];
}
System.out.println("Max is " + max);
}
}
This would produce the following result:
1.9
2.9
3.4
3.5
Total is 11.7
Max is 3.5
The foreach Loops:
JDK 1.5 introduced a new for loop known as foreach loop or enhanced
for loop, which enables you to traverse the complete array sequentially
without using an index variable.
Example:
The following code displays all the elements in the array myList:
public class TestArray {
public static void main(String[] args) {
double[] myList = {1.9, 2.9, 3.4, 3.5};
// Print all the array elements
for (double element: myList) {
System.out.println(element);
}
}
}
This would produce the following result:
1.9
2.9
3.4
3.5
Passing Arrays to Methods:
Just as you can pass primitive type values to methods, you can also
pass arrays to methods. For example, the following method displays the
elements in an int array:
public static void printArray(int[] array)
{
for (int i = 0; i < array.length; i++)
{
System.out.print(array[i] + " ");
}
}
You can invoke it by passing an array. For example, the following
statement invokes the printArray method to display 3, 1, 2, 6, 4, and 2:
printArray(new int[]{3, 1, 2, 6, 4, 2});
Returning an Array from a Method:
A method may also return an array. For example, the method shown below returns an array that is the reversal of another array:
public static int[] reverse(int[] list)
{
int[] result = new int[list.length];
for (int i = 0, j = result.length - 1; i < list.length; i++, j--)
{
result[j] = list[i];
}
return result;
}
I hope this post will help you.
Thanks !!
If still you have some query regarding to this then please post your comment after that i will 100% help you…:)
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