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Is there any distinction between int[] a and int a[] in Java?


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An array in Java is a group of like-typed variables referred to by a common name. Arrays in Java work differently than they do in C/C++.  In Java, Array can be declared in the following ways:

One-Dimensional Arrays: The general form of a one-dimensional array declaration is 

type var-name[];
OR
type[] var-name;

Multidimensional Arrays:

int[][] intArray = new int[10][20]; //a 2D array or matrix
int[][][] intArray = new int[10][20][10]; //a 3D array

Difference between “int[] a” and “int a[]” for 1-D Arrays in Java

For 1-D Array, in Java, there is no difference and any of the mentioned syntaxes can be used to declare a 1-D array.

For example:

Java

  

class GFG {

    public static void main(String[] args)

    {

        

        

        int[] arr1;

        arr1 = new int[5];

        arr1[0] = 10;

        arr1[1] = 20;

        arr1[2] = 30;

        arr1[3] = 40;

        arr1[4] = 50;

  

        

        

        for (int i = 0; i < arr1.length; i++)

            System.out.println("Array from method 1: "

                               + arr1[i]);

        System.out.println();

  

        

        

        int arr2[];

        arr2 = new int[5];

        arr2[0] = 1;

        arr2[1] = 2;

        arr2[2] = 3;

        arr2[3] = 4;

        arr2[4] = 5;

  

        

        

        for (int i = 0; i < arr2.length; i++)

            System.out.println("Array from method 2: "

                               + arr2[i]);

    }

}

Output

Array from method 1: 10
Array from method 1: 20
Array from method 1: 30
Array from method 1: 40
Array from method 1: 50

Array from method 2: 1
Array from method 2: 2
Array from method 2: 3
Array from method 2: 4
Array from method 2: 5

Difference between “int[] a” and “int a[]” for multiple Array declarations in Java

While declaring multiple Arrays in Java at the same time, the method of declaration is important and needs to follow the proper syntax. If not, it will result in compile-time errors.

  • Correct syntax to declare multiple arrays
    int []a, b;

    For example:

    Java

      

    import java.io.*;

      

    class GFG {

        public static void main(String[] args)

        {

            int[] a, b;

            

            a = new int[3];

            b = new int[4];

            System.out.print("array a: ");

            for (int i = 0; i < 3; i++) {

                a[i] = i;

                System.out.print(a[i] + " ");

            }

            System.out.print("n");

            System.out.print("array b: ");

      

            for (int i = 0; i < 4; i++) {

                b[i] = i;

                System.out.print(b[i] + " ");

            }

        }

    }

    Output

    array a: 0 1 2 
    array b: 0 1 2 3 
  • Incorrect Declaration of multiple arrays
    int a[], b;
    int a, b[];

    Example 1: Example to show output for int a[], b declaration.

    While using int a[], b method to declare multiple arrays in Java, the compiler will declare “a” as an array, whereas “b” will be declared as an integer variable. Hence while accessing this will give a compiler error.

    Java

      

    import java.io.*;

      

    class GFG {

        public static void main(String[] args)

        {

      

            

            

            

            

            

            

            

            int a[], b;

      

            b = new int[4];

            a = new int[3];

            System.out.print("array a: ");

            for (int i = 0; i < 3; i++) {

                a[i] = i;

                System.out.print(a[i] + " ");

            }

            System.out.print("n");

            System.out.print("array b: ");

      

            for (int i = 0; i < 4; i++) {

                b[i] = i;

                System.out.print(b[i] + " ");

            }

        }

    }

    Compile Time Error Messages:

    prog.java:19: error: incompatible types: int[] cannot be converted to int
            b = new int[4];
                ^
    prog.java:30: error: array required, but int found
                b[i] = i;
                 ^
    prog.java:31: error: array required, but int found
                System.out.print(b[i] + " ");
                                  ^
    3 errors

    Example 2: Example to show output for int a, b[] declaration.

    While using int a, b[] method to declare multiple arrays in Java, the compiler will declare “a” as an integer variable, whereas “b” will be declared as an integer array. Hence while accessing this will give a compiler error.

    Java

      

    import java.io.*;

      

    class GFG {

        public static void main(String[] args)

        {

      

            

            

            

            

            

            

            

            int a, b[];

      

            b = new int[4];

            a = new int[3];

            System.out.print("array a: ");

            for (int i = 0; i < 3; i++) {

                a[i] = i;

                System.out.print(a[i] + " ");

            }

            System.out.print("n");

            System.out.print("array b: ");

      

            for (int i = 0; i < 4; i++) {

                b[i] = i;

                System.out.print(b[i] + " ");

            }

        }

    }

    Compile Time Error Messages:

    prog.java:19: error: incompatible types: int[] cannot be converted to int
            b = new int[4];
                ^
    prog.java:30: error: array required, but int found
                b[i] = i;
                 ^
    prog.java:31: error: array required, but int found
                System.out.print(b[i] + " ");
                                  ^
    3 errors

Difference between “int[] a” and “int a[]” for Multidimensional Arrays in Java

For Multidimensional Arrays, in Java, there is no difference and any of the mentioned syntaxes can be used for declaration.

For example:

Java

public class multiDimensional {

    public static void main(String args[])

    {

        

        

        int[][] arr1

            = { { 2, 7, 9 }, { 3, 6, 1 }, { 7, 4, 2 } };

  

        

        for (int i = 0; i < 3; i++) {

            for (int j = 0; j < 3; j++)

                System.out.print(arr1[i][j] + " ");

  

            System.out.println();

        }

        System.out.println();

  

        

        

        int arr2[][] = { { 10, 20, 30 }, { 40, 50, 60 } };

  

        

        for (int i = 0; i < 2; i++) {

            for (int j = 0; j < 3; j++)

                System.out.print(arr2[i][j] + " ");

  

            System.out.println();

        }

    }

}

Output

2 7 9 
3 6 1 
7 4 2 

10 20 30 
40 50 60 

Which is more preferred syntax among “int[] a” and “int a[]” to declare an array?

  • Though, there is no difference in functionality between both types of declaration. Both declare an array of integers, thus, there is no conclusion which style is more preferable, int[] a is the preferred syntax to declare an array in Java whereas int a[] was included to help the traditional C/C++ programmers.
  • Technically, both syntaxes are the same in the case of declaring a single array. But both declarations give different results if we declare multiple arrays in a single statement.

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