An array is a collection of similar type of elements which has contiguous memory location.
Java
array is an object which contains elements of a similar
data type. The elements of an array are stored in a contiguous memory location.
It is a data structure where similar elements are stored.
Arrays in Java work differently than they do in
C/C++. Following are some important points about Java arrays.
- In Java all arrays are dynamically allocated.
- Since arrays are objects in Java, we can find their length using the
object property length. This is different from C/C++ where we
find length using sizeof .
- A Java array variable can also be declared like other variables with
[] after the data type.
- The variables in the array are ordered and each have an index
beginning from 0.
- Java array can be also be used as a static field, a local variable
or a method parameter.
- The size of an array must be specified by an int or
short value and not long.
- The direct superclass of an array type is Object.
- Every array type implements the interfaces Cloneable and java.io.Serializable.
Types
of Array in java
There are two types of array.
- Single Dimensional Array
- Multidimensional Array
One-Dimensional
Arrays :
The general form of a one-dimensional array declaration is
type var-name[];
OR
type[] var-name;
An array declaration has two components: the type and the name. type declares
the element type of the array. The element type determines the data type of
each element that comprises the array.
Instantiating an
Array in Java
When an array is declared, only a reference of array is created. To
actually create or give memory to array, an array is created like :
var-name = new type [size];
Here, type specifies the type of data being
allocated, size specifies the number of elements in the array,
and var-name is the name of array variable that is linked to
the array.
Example:
int intArray[]; //declaring
array
intArray = new int[20]; //
allocating memory to array
OR
int[] intArray = new int[20]; // combining both statements in one
Accessing Java
Array Elements using for Loop
Each element in the array is accessed using its index. The index begins
with 0 and ends at (total array size)-1. All the elements of array can be
accessed using for Loop.
// accessing the elements of the specified array
for (int i = 0; i < arr.length; i++)
System.out.println("Element
at index " + i + " : "+ arr[i]);
Multidimensional
Arrays
Multidimensional arrays are arrays of arrays with each
element of the array holding the reference of other array. These are also known
as Jagged Arrays.
A multidimensional array is created by appending one set of square
brackets ([]) per dimension.
int[][] intArray = new int[10][20]; //a 2D array or matrix
int[][][] intArray = new int[10][20][10]; //a 3D array
for example an array
int arr[][] = { {2,7,9},{3,6,1},{7,4,2} };
is represented like
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