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Can We Reverse an Array in Java?

An Array is given to you. Your task would be to Reverse that Array in Java

Have you ever encountered any such problem? A mere read would give you an idea that the given problem is related to array reversal. Array data structure is the collection of certain items that are stored in the contiguous memory locations. The idea in this case would be to store the multiple items which are of the same type.

Reverse an array is an important question that is often asked from the candidates of a coding interview. This is a crucial java topic that holds a great importance and which needs certain approaches that you should follow to solve the array related problems.


Be on the Pace and Read this Blog Till the End!

If you are a budding programmer, you may often encounter questions on the topics of reversing arrays, reversing the string, reverse nodes in k group and other related questions. In the case of reversing an array, you need to reverse an array in such a way so that the first elements of a given array gets placed at its last position and the second elements gets placed at the respective second last positions and so on till the last element would come at its first index.

Though, in the case of java, primitive arrays including int, strings or double arrays are needed to be reversed for the aim to get the specific codes. For that you can also make use of the java.util.arrays as the primitive class in order to reverse the given array.


Approaches to Follow

There are numerous approaches which you can follow in order to reverse an array in java. You can either write the function with the help of a traditional for loop or can swap all the elements until your given array gets sorted. All of these approaches are discussed as below:

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Using Temp Array

The first method to use would be the temp array method which you can follow:

  • Take the size of an array as the input and the elements of an array
  • Consider a given function reverse which will take the parameter as – the array [ like arr] and the size of a given array [ denoted as n]
  • Inside this function, any new array [ with the size of the first array i.e arr] would be initialised. The arr [] would be iterated with its first element by picking each element as the arr[] to place it in the new array from the back.
  • By following the instructions, all the elements in an array arr [] would be placed in the recursive order in a given new array
  • Further, it would be easy for you to iterate through any new array from the start so as to print all the array elements


Using Swapping

The second method also makes use of the similar code in order to input and print a particular array. However, in this case, you may not need to create a new array like that of the previous method. This method swaps all the elements in a given array. The first element will be first swapped with that of the last element. The second element would be swapped with the last and so on.

For example; consider a given array [ 1, 2, 3, n-2 n-1 ….. N]

We can swap it either with the n, 2 or with n -1 and 3 with n-2 by going further.


Reverse an Array with the Help of Array list

You can reverse an array in java with the help of the reverse method in any collection framework. You may first in this case need to convert the given array with the list of ‘reverse’ methods so as to take up the list of special arguments. With the help of a program, you can easily define a string array. Though, by converting it into a list, you can easily revere the array.


Reversing the Given Array using the Traditional for Loop Function

Yet another method, which we can use to reverse an array is to write a special method for the array reversal. In this method, you will be having a new array in which you are required to put the element of an original array into a new array in the reverse order. With the help of a reverse function, you can easily reverse the elements of an array by displaying them in the reverse order.


In-Place Reversal of the Array

This is yet another method for reversing an array. You need to reverse all the elements in an array in-place without using any type of separate array. For this method, the first element of your array would be swapped with that of the last element in a given array. Similarly, in this case, the second element in an array would be swapped with that of the second last element present in your array and further. This way you will reach at the end of your array reversal, where you may need to traverse the entire array.


Arrayutils.Reverse ()

Apache commons is a library function which is useful for java development. This library is most often added default by the coders in their projects so as to view the complementary JDK.

It involves the overloaded reverse() approach that will cause the reverse of an int, float or the object types array in the java program. This method easily reverses a given array as no new array will be needed in this case for the reversal of array in java.


Wrapping Up

When you are entering the java universe, you may often encounter some of the most essential concepts like reverse an array, reversing any given string, reverse nodes in k group and other such related concepts.

In this blog post, we have discussed reversing an array and its various approaches in java. Bookmark these techniques for array reversal and broaden your knowledge base in an ideal way!