Java Online Compiler
Example: Reverse Array Using Collections.reverse() in Java
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Main.java
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// Reverse Array Using Collections.reverse() import java.util.ArrayList; import java.util.Arrays; import java.util.Collections; import java.util.List; public class Main { public static void main(String[] args) { // Step 1: Declare and initialize the original array (primitive type) int[] originalIntArray = {11, 22, 33, 44}; System.out.println("Original int[]: " + Arrays.toString(originalIntArray)); // Step 2: Convert primitive int[] to List<Integer> List<Integer> list = new ArrayList<>(); for (int i : originalIntArray) { list.add(i); } System.out.println("Converted List: " + list); // Step 3: Use Collections.reverse() to reverse the list Collections.reverse(list); // Step 4: Print the reversed list System.out.println("Reversed List: " + list); // Step 5: (Optional) Convert the reversed list back to an int[] if needed int[] reversedIntArray = new int[list.size()]; for (int i = 0; i < list.size(); i++) { reversedIntArray[i] = list.get(i); } System.out.println("Reversed int[] (from list): " + Arrays.toString(reversedIntArray)); // --- Example with an Integer array directly (no primitive conversion needed initially) --- Integer[] integerArray = {100, 200, 300}; System.out.println("\nOriginal Integer[]: " + Arrays.toString(integerArray)); List<Integer> integerList = Arrays.asList(integerArray); // Convert Integer[] to List directly // Note: Arrays.asList returns a fixed-size list. If you need to modify its structure (add/remove), // wrap it in a new ArrayList: List<Integer> modifiableList = new ArrayList<>(Arrays.asList(integerArray)); Collections.reverse(integerList); System.out.println("Reversed Integer List: " + integerList); System.out.println("Original (now reversed) Integer[]: " + Arrays.toString(integerArray)); // original array is also reversed } }
Output
Clear
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