This seems very simple but I can’t quite figure out why this isn’t working.
I want to reverse the elements in my LinkedList which I have a working method for, but I can’t return the value as my prof wants it to be a void method. How would I go about this?
import java.util.LinkedList;
public class ListUtil {
public static void reverse(LinkedList<String> strings) {
LinkedList<String> reverseLinkedList = new LinkedList<>();
for(int i = strings.size() - 1; i >= 0; i--) {
reverseLinkedList.add(strings.get(i));
}
strings = reverseLinkedList;
System.out.println(strings);
}
}
import java.util.LinkedList;
public class ReverseTester {
public static void main(String[] args) {
LinkedList<String> employeeNames = new LinkedList<>();
employeeNames.addLast("Dick");
employeeNames.addLast("Harry");
employeeNames.addLast("Romeo");
employeeNames.addLast("Tom");
ListUtil.reverse(employeeNames);
System.out.println(employeeNames);
System.out.println("Expected: [Tom, Romeo, Harry, Dick]");
}
}
In my ListUtil class, it does reverse the list, but doesnt return a value (as it is void) but I don’t know how to go about setting employeeName in the ReverseTester class.
I know this is probably super simple but I have not been able to figure this out for the life of me, any help is greatly appreciated.
Answer
Empty and re-fill the existing list rather than replacing it.
public static void reverse(LinkedList<String> strings) {
List<String> temp = new ArrayList<>(strings); // Copy the contents of the original list. Pass the original list to constructor of our duplicate list.
strings.clear(); // Empty the original list.
for (String e : temp)
strings.addFirst(e); // Refill the original list using elements from our duplicate list.
}
Or simply
public static void reverse(LinkedList<String> strings) {
Collections.reverse(strings);
}