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Implementing a sort checker application

You're implementing a method to check if an ArrayList of integers is sorted in ascending order. The current implementation compares every possible pair of elements in the list to ensure they are in the correct order.

This exercise is part of the course

Optimizing Code in Java

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Exercise instructions

  • Iterate through all the numbers in numbers.
  • Iterate through all the numbers in numbers again.
  • Return when you have not found a pair in wrong order.

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        // Edit this number to see how it affects execution time
        int arraySize = 1000;
        
        ArrayList unsortedNumbers = new ArrayList<>();
        for (int i = 0; i < arraySize; i++) {
            unsortedNumbers.add(i);
        }
        int temp = unsortedNumbers.get(arraySize - 1);
        unsortedNumbers.set(arraySize - 1, unsortedNumbers.get(arraySize - 2));
        unsortedNumbers.set(arraySize - 2, temp);
        
        SortChecker checker = new SortChecker();
	    boolean result = checker.isSorted(unsortedNumbers);
        
        System.out.println("Unsorted array result: " + result);
    }
}

class SortChecker {
    public boolean isSorted(ArrayList numbers) {
        // Iterate through all the numbers
        for (____) {
            // Iterate through all the numbers again
            for (____) {
                if (numbers.get(i) > numbers.get(j)) {
                    return false;
                }
            }
        }
        // Return if we have not returned false so far
        return ____;
    }
}
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