To reverse an int array, you swap items up until you reach the midpoint, like this:
for(int i = 0; i < validData.length / 2; i++)
{
int temp = validData[i];
validData[i] = validData[validData.length - i - 1];
validData[validData.length - i - 1] = temp;
}
The way you are doing it, you swap each element twice, so the result is the same as the initial list.
Answer from 3lectrologos on Stack Overflow Top answer 1 of 16
357
To reverse an int array, you swap items up until you reach the midpoint, like this:
for(int i = 0; i < validData.length / 2; i++)
{
int temp = validData[i];
validData[i] = validData[validData.length - i - 1];
validData[validData.length - i - 1] = temp;
}
The way you are doing it, you swap each element twice, so the result is the same as the initial list.
2 of 16
338
With Commons.Lang, you could simply use
ArrayUtils.reverse(int[] array)
Most of the time, it's quicker and more bug-safe to stick with easily available libraries already unit-tested and user-tested when they take care of your problem.
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Does Java provide a built-in method to reverse an array?
Javaโs standard libraries do not include a direct method for reversing primitive arrays. However, you can convert the array to a List, by using Collections.reverse(), then convert it back, which works for arrays of object references.
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Comprehensive Guide to Reversing an Array in Java
What is the best way to reverse an array in Java?
An in-place approach using two pointers is often considered the best because it swaps elements from both ends of the array without extra memory, runs in O(n) time, and is straightforward to implement.
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Comprehensive Guide to Reversing an Array in Java
How do I reverse an array in Java 8 using streams?
You can convert the array to a stream, collect it into a list, and then use Collections.reverse(). Alternatively, map the array to an IntStream (for primitives) or Stream (for objects), then reverse the collection after accumulation.
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Comprehensive Guide to Reversing an Array in Java
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Reverse an Array in Java - Scaler Topics
April 28, 2024 - In the above example, the array A1 contains the elements [1, 2, 3, 4, 5]. On reversing this array, we get an array A2, i.e., [5, 4, 3, 2, 1]. Note how the element 3, present in the middle of the array, remains in place.
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Comprehensive Guide to Reversing an Array in Java
April 1, 2025 - Array Reversal is the process of taking an array (a list of elements) and flipping the order of its contents. Let's take an example, if you have an array(1,2,3,4,5), reversing it results: in (5,4, 3,2,1).
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Reverse an array in java (Beginning Java forum at Coderanch)
Output of my program: 7 random digits myArray[0] = 5 myArray[1] = 14 myArray[2] = 88 myArray[3] = 18 myArray[4] = 20 myArray[5] = 8 myArray[6] = 46 myArray[7] = 100 After reversing the array myArray[0] = 100 myArray[1] = 46 myArray[2] = 8 myArray[3] = 20 myArray[4] = 20 myArray[5] = 8 myArray[6] ...
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Java Arrays Reverse Example
September 1, 2008 - Following example reverses an array list by using Collections.reverse(ArrayList)method. import java.util.ArrayList; import java.util.Collections; public class Main { public static void main(String[] args) { ArrayList arrayList = new ArrayList(); arrayList.add("A"); arrayList.add("B"); arrayList.add("C"); arrayList.add("D"); arrayList.add("E"); System.out.println("Before Reverse Order: " + arrayList); Collections.reverse(arrayList); System.out.println("After Reverse Order: " + arrayList); } }
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Reverse Array Java Example - Java Code Geeks
February 7, 2022 - You can reverse an array by converting an array to ArrayList and then reverse the ArrayList or use the Apache Commons ArrayUtils.reverse().
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Reverse a given Array - Tutorial
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Java - Iterate Array in Reverse Order - GeeksforGeeks
July 23, 2025 - // Java Program to iterate over an array // in reverse order using enhanced for loop import java.util.*; public class Main { public static void main(String[] args) { // Array initialization Integer[] arr = {10, 20, 30, 40, 50}; // Reversing ...
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[Solved] 3 Examples to reverse an Array in Java - Example Tutorial | Java67
This is another simple way to reverse an array in Java is by first converting the array to List and then using the Collections.reverse() method to reverse the ArrayList. This method takes a List and reverses the element in linear time. You should use this approach if you need to reverse an array in your project. You can reverse int, String, or any type of array by using this method. Let's see an example of reversing a String array in Java:
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Java Program to print the elements of an array in reverse order - Javatpoint
Java Program to print the elements of an array in reverse order - Java Program to print the elements of an array in reverse order on fibonacci, factorial, prime, armstrong, swap, reverse, search, sort, stack, queue, array, linkedlist, tree, graph, pattern, string etc.
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Reverse an Array in Java - 4 Methods with Code
April 25, 2023 - Time Complexity: The time complexity of this approach is O(N) as we have to traverse the array. Space Complexity (Auxiliary Space): The auxiliary space used is O(1) as we have not used any extra space. In Java, the method reverse() in the Class Collections is used to reverse collections like ...
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3 Methods to Reverse an Array in Java
This particular method of array reverse in Java converts the given array into an ArrayList and then utilizes the Collections.reverse() method that takes up the items in the list and reverses the elements in linear time. Arrays of int, string or other types can be reversed with the help of this method.The following example depicts a reversal of a string type array in Java:
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Java Program to reverse the Array
On the second * iteration i is ... last. */ j = i - 1; i = 0; scanner.close(); while(i<j) { temp = number[i]; number[i] = number[j]; number[j] = temp; i++; j--; } System.out.print("Reversed array: "); for(i=0; i<counter; i++) { System.out.print(number[i]+ " "); } } }...
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How to Reverse an Array in place in Java? Example Solution | Java67
In the last section, I have explained to you the logic or algorithm to reverse an array in place, now is the time to convert that algorithm into pseudo-code and then real code in Java. You will also calculate the time and space complexity of our solution, which is often required in Interviews as well as in the real world to meet your performance SLA. So, let's see an example of how you can reverse an array of String in Java in place.