How to compare arrays in Java? How to use Final and Jagged array?

Unlike C++ an arrays are first class objects in the Java.

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An easy way is to run a loop and compare elements one by one. Java provides a direct method Arrays.equals() to compare two arrays. There is a list of equals() methods in Arrays class for different primitive types (int, char, ..etc) and one for Object type (which is base of all classes in Java).

import java.util.Arrays;
class Test
{
public static void main (String[] args)
{
int arr1[] = {1, 2, 3};
int arr2[] = {1, 2, 3};
if (Arrays.equals(arr1, arr2))
System.out.println("Same");
else
System.out.println("Different");
}
}

Deep comparison of array contents

Arrays.equals() is not able to do deep comparison but Java provides another method for this Arrays.deepEquals() which does deep comparison.

import java.util.Arrays;
class Test
{
public static void main (String[] args)
{
int inarr1[] = {1, 2, 3};
int inarr2[] = {1, 2, 3};
Object[] arr1 = {inarr1};
arr2 = {inarr2};
if (Arrays.deepEquals(arr1, arr2))
System.out.println("Same");
else
System.out.println("Different");
}
}

Final arrays in Java

The array arr is declared as final, but the elements of array are changed without any problem. Arrays are objects and object variables are always references in Java.

class Test
{
public static void main(String args[])
{
final int arr[] = {1, 2, 3, 4, 5};
// Note: arr is final
for (int i = 0; i < arr.length; i++)
{
arr[i] = arr[i]*10;
System.out.println(arr[i]);
}
}
}

Run the code on IDE to check the output.

class Test
{
int p = 20;
public static void main(String args[])
{
final Test t = new Test();
t.p = 30;
System.out.println(t.p);
}
}

Jagged Arrays in Java

Jagged array is array of arrays such that member arrays can be of different sizes, we can create a 2-D arrays but with variable number of columns in each row. These type of arrays are also known as Jagged arrays.

class Main
{
public static void main(String[] args)
{
int arr[][] = new int[2][]; // Making array Jagged
arr[0] = new int[3];
arr[1] = new int[2];
int count = 0;
for (int i=0; iarr[i][j]=count++;
System.out.println("Contents of 2D Jagged Array");
for (int i=0; i{
for (int j=0; jSystem.out.print(arr[i][j] + " ");
System.out.println();
}
}
}

Run the code on IDE to check the output.

array comparison

Final array

Jagged array

Java

Ayesha

Tech writer at newsandstory