Java Array
Normally, array is a collection
of similar type of elements that have contiguous memory location.
Java array is an object the contains elements of
similar data type. It is a data structure where we store similar elements. We
can store only fixed set of elements in a java array.
Array in java is index based,
first element of the array is stored at 0 index.
Advantage of Java Array
- Code
Optimization: It makes the
code optimized, we can retrieve or sort the data easily.
- Random
access: We can get any
data located at any index position.
Disadvantage of Java Array
- Size
Limit: We can store
only fixed size of elements in the array. It doesn't grow its size at
runtime. To solve this problem, collection framework is used in java.
Types of Array in java
There are two types of array.
- Single
Dimensional Array
- Multidimensional
Array
Single Dimensional Array in java
Syntax to Declare an Array in java
1. dataType[] arr; (or)
2. dataType []arr; (or)
3. dataType arr[];
Instantiation of an Array in java
1.
arrayRefVar=new datatype[size];
Example of
single dimensional java array
Let's see the simple example of
java array, where we are going to declare, instantiate, initialize and traverse
an array.
1.
class Testarray{
2.
public static void main(String args[]){
3.
4.
int a[]=new int[5];//declaration and instantiation
5.
a[0]=10;//initialization
6.
a[1]=20;
7.
a[2]=70;
8.
a[3]=40;
9.
a[4]=50;
10.
11. //printing array
12. for(int i=0;i<a.length;i++)//length is the property of array
13. System.out.println(a[i]);
14.
15. }}
Output: 10
20
70
40
50
Declaration,
Instantiation and Initialization of Java Array
We can declare, instantiate and
initialize the java array together by:
1. int a[]={33,3,4,5};//declaration, instantiation and initialization
Let's see the simple example to
print this array.
1.
class Testarray1{
2.
public static void main(String args[]){
3.
4.
int a[]={33,3,4,5};//declaration, instantiation and initialization
5.
6.
//printing array
7.
for(int i=0;i<a.length;i++)//length is the property of array
8.
System.out.println(a[i]);
9.
10. }}
Output:33
3
4
5
Passing Array to method in java
We can pass the java array to
method so that we can reuse the same logic on any array.
Let's see the simple example to
get minimum number of an array using method.
1. class Testarray2{
2. static void min(int arr[]){
3. int min=arr[0];
4. for(int i=1;i<arr.length;i++)
5. if(min>arr[i])
6. min=arr[i];
7.
8. System.out.println(min);
9. }
10.
11. public static void main(String args[]){
12.
13. int a[]={33,3,4,5};
14. min(a);//passing array to method
15.
16. }}
Output:3
Multidimensional array in java
In such case, data is stored in
row and column based index (also known as matrix form).
Syntax to Declare Multidimensional Array in java
1.
dataType[][] arrayRefVar; (or)
2.
dataType [][]arrayRefVar; (or)
3.
dataType arrayRefVar[][]; (or)
4.
dataType []arrayRefVar[];
Example to instantiate Multidimensional Array in java
1.
int[][] arr=new int[3][3];//3 row and 3 column
Example to initialize Multidimensional Array in java
1.
arr[0][0]=1;
2.
arr[0][1]=2;
3.
arr[0][2]=3;
4.
arr[1][0]=4;
5.
arr[1][1]=5;
6.
arr[1][2]=6;
7.
arr[2][0]=7;
8.
arr[2][1]=8;
9.
arr[2][2]=9;
Example of
Multidimensional java array
Let's see the simple example to
declare, instantiate, initialize and print the 2Dimensional array.
1.
class Testarray3{
2.
public static void main(String args[]){
3.
4.
//declaring and initializing 2D array
5.
int arr[][]={{1,2,3},{2,4,5},{4,4,5}};
6.
7.
//printing 2D array
8.
for(int i=0;i<3;i++){
9.
for(int j=0;j<3;j++){
10. System.out.print(arr[i][j]+" ");
11. }
12. System.out.println();
13. }
14.
15. }}
Output:1 2 3
2 4 5
4 4 5
What is class name of java array?
In java, array is an object.
For array object, an proxy class is created whose name can be obtained by
getClass().getName() method on the object.
1.
class Testarray4{
2.
public static void main(String args[]){
3.
4.
int arr[]={4,4,5};
5.
6.
Class c=arr.getClass();
7.
String name=c.getName();
8.
9.
System.out.println(name);
10.
11. }}
Output:I
Copying a java array
We can copy an array to another
by the arraycopy method of System class.
Syntax of arraycopy method
1.
public static void arraycopy(
2.
Object src, int srcPos,Object dest, int destPos, int length
3.
)
Example of arraycopy method
1.
class TestArrayCopyDemo {
2.
public static void main(String[] args) {
3.
char[] copyFrom = { 'd', 'e', 'c', 'a', 'f', 'f', 'e',
4.
'i', 'n', 'a', 't', 'e', 'd' };
5.
char[] copyTo = new char[7];
6.
7.
System.arraycopy(copyFrom, 2, copyTo, 0, 7);
8.
System.out.println(new String(copyTo));
9.
}
10. }
Output:caffein
Addition of 2 matrices in java
Let's see a simple example that
adds two matrices.
1.
class Testarray5{
2.
public static void main(String args[]){
3.
//creating two matrices
4.
int a[][]={{1,3,4},{3,4,5}};
5.
int b[][]={{1,3,4},{3,4,5}};
6.
7.
//creating another matrix to store the sum of two matrices
8.
int c[][]=new int[2][3];
9.
10. //adding and printing addition of 2 matrices
11. for(int i=0;i<2;i++){
12. for(int j=0;j<3;j++){
13. c[i][j]=a[i][j]+b[i][j];
14. System.out.print(c[i][j]+" ");
15. }
16. System.out.println();//new line
17. }
18.
19. }}
Output:2 6 8
6 8 10
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