Single and Multidimensional arrays in java


 


Java Arrays

Single and multidimensional arrays in java

Normally, 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. 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 size of 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++.

Java array

Advantages

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

Disadvantages

  • 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.

    • 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 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[5];//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. //traversing 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. //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 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

  • 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

    Passing Array to a 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 the minimum number of an array using a method.

    1. //Java Program to demonstrate the way of passing an array  
    2. //to method.  
    3. class Testarray2{  
    4. //creating a method which receives an array as a parameter  
    5. static void min(int arr[]){  
    6. int min=arr[0];  
    7. for(int i=1;i<arr.length;i++)  
    8.  if(min>arr[i])  
    9.   min=arr[i];  
    10.   
    11. System.out.println(min);  
    12. }  
    13.   
    14. public static void main(String args[]){  
    15. int a[]={33,3,4,5};//declaring and initializing an array  
    16. min(a);//passing array to method  
    17. }}  

  • Output:

    3

    Anonymous Array in Java

    Java supports the feature of an anonymous array, so you don't need to declare the array while passing an array to the method.

    1. //Java Program to demonstrate the way of passing an anonymous array  
    2. //to method.  
    3. public class TestAnonymousArray{  
    4. //creating a method which receives an array as a parameter  
    5. static void printArray(int arr[]){  
    6. for(int i=0;i<arr.length;i++)  
    7. System.out.println(arr[i]);  
    8. }  
    9.   
    10. public static void main(String args[]){  
    11. printArray(new int[]{10,22,44,66});//passing anonymous array to method  
    12. }}  

  • Returning Array from the Method

    We can also return an array from the method in Java.

    1. //Java Program to return an array from the method  
    2. class TestReturnArray{  
    3. //creating method which returns an array  
    4. static int[] get(){  
    5. return new int[]{10,30,50,90,60};  
    6. }  
    7.   
    8. public static void main(String args[]){  
    9. //calling method which returns an array  
    10. int arr[]=get();  
    11. //printing the values of an array  
    12. for(int i=0;i<arr.length;i++)  
    13. System.out.println(arr[i]);  
    14. }}  

  • Output:

    10
30
50
90
60

    ArrayIndexOutOfBoundsException

    The Java Virtual Machine (JVM) throws an ArrayIndexOutOfBoundsException if length of the array in negative, equal to the array size or greater than the array size while traversing the array.

    1. //Java Program to demonstrate the case of   
    2. //ArrayIndexOutOfBoundsException in a Java Array.  
    3. public class TestArrayException{  
    4. public static void main(String args[]){  
    5. int arr[]={50,60,70,80};  
    6. for(int i=0;i<=arr.length;i++){  
    7. System.out.println(arr[i]);  
    8. }  
    9. }}  

  • Output:

    Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 4
	at TestArrayException.main(TestArrayException.java:5)
50
60
70
80

    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[]){  
    4. //declaring and initializing 2D array  
    5. int arr[][]={{1,2,3},{2,4,5},{4,4,5}};  
    6. //printing 2D array  
    7. for(int i=0;i<3;i++){  
    8.  for(int j=0;j<3;j++){  
    9.    System.out.print(arr[i][j]+" ");  
    10.  }  
    11.  System.out.println();  
    12. }  

  • Output:

    1 2 3
2 4 5
4 4 5

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