Arrays and strings

Java Arrays
Normally, an array is a collection of similar type of(homogeneous) elements which have
a contiguous memory location.

Java array is an object which contains elements of a similar data type. Additionally, The
elements of an array are stored in a contiguous memory location. It is a data structure
where we store similar elements. We can store only a fixed set of elements in a Java
array.

Array in Java is index-based, the first element of the array is stored at the 0th index,
2nd element is stored on 1st index and so on.

Unlike C/C++, we can get the length of the array using the length member. In C/C++,
we need to use the sizeof operator.

In Java, array is an object of a dynamically generated class. Java array inherits the
Object class, and implements the Serializable as well as Cloneable interfaces. We can
store primitive values or objects in an array in Java. Like C/C++, we can also create
single dimensional or multidimensional arrays in Java.

Moreover, Java provides the feature of anonymous arrays which is not available in
C/C++.




Advantages
o Code Optimization: It makes the code optimized, we can retrieve or sort the
data efficiently.
o Random access: We can get any data located at an index position.


Disadvantages
o Size Limit: We can store only the 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 which grows automatically.




Types of Array in java
There are two types of array.

, o Single Dimensional Array
o Multidimensional Array


Single Dimensional Array in Java
Syntax to Declare an Array in Java

1. dataType[] arr; (or) eg. int[] arr1;
2. dataType []arr; (or) eg. Int []arr1;
3. dataType arr[]; eg. Int arr1[];

Instantiation of an Array in Java

1. arrayRefVar=new datatype[size];

eg.int arr1[] = new int[5];


Example of Java Array
Let's see the simple example of java array, where we are going to declare, instantiate,
initialize and traverse an array.

1. //Java Program to illustrate how to declare, instantiate, initialize
2. //and traverse the Java array.
3. class Testarray{
4. public static void main(String args[]){
5. int a[]=new int[7];//declaration and instantiation


6. a[0]=10;//initialization
7. a[1]=20;
8. a[2]=70;
9. a[3]=40;
10. a[4]=50;
11.
12. //traversing array
13. for(int i=0;i<a.length;i++)//length is the property of array
14. System.out.println(a[i]);
15. }

16. }

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. //Java Program to illustrate the use of declaration, instantiation
2. //and initialization of Java array in a single line
3. class Testarray1{
4. public static void main(String args[]){
5. int a[]={33,3,4,5};//declaration, instantiation and initialization
6. //printing/accessing array
7. for(int i=0;i<a.length;i++)//length is the property of array
8. System.out.println(a[i]);
9. }}

Output:

33
3
4
5


For-each Loop for Java Array
We can also print the Java array using for-each loop. The Java for-each loop prints the
array elements one by one. It holds an array element in a variable, then executes the
body of the loop.

The syntax of the for-each loop is given below:

1. for(data_type variable:array){
2. //body of the loop
3. }

Let us see the example of print the elements of Java array using the for-each loop.

1. //Java Program to print the array elements using for-each loop
2. class Testarray1{
3. public static void main(String args[]){
4. int arr[]={33,3,4,5};
5. //printing array using for-each loop

, 6. for(int i:arr)
7. System.out.println(i);
8. }}

Output:

33
3
4
5




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. //Java Program to illustrate the use of multidimensional array
2. class Testarray3{
3. public static void main(String args[]){