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
Int [4]={10,20,30,40}=0,1,2,3
Char[9]={‘a’,’b’,’c’……}
|
0=10
|
1=20
|
2=30
|
3=40
|
- 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
|
0=10
|
1=20
|
2=30
|
3=40
|
1. dataType[] arr; (or)
2. dataType []arr; (or)
3.
dataType arr[];
4.
int[4] arr={10,20,30,40}
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;
//printing array
for(int i=0;i<a.length;i++)//length is the property of array
System.out.println(a[i]);
}}
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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