Undo last action in a text editor

Many text editors allow users to navigate backward through changes and insert missing words when needed. Using ListIterator, you can move backward through a list of actions and insert corrections where necessary.

In this exercise, you will traverse a list of words in reverse, and if you find "error", you will insert correction before it, simulating an undo operation in a text editor.

This exercise is part of the course

Input/Output and Streams in Java

View Course

Exercise instructions

Create a ListIterator object for the textHistory list, starting from the end.
Check if more previous elements are available in textHistory list.
Retrieve previous element and move ListIterator backward
Insert new element correction before element error

Hands-on interactive exercise

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

import java.util.ArrayList;
import java.util.ListIterator;

public class TextEditorUndo {
    public static void main(String[] args) {
        ArrayList textHistory = new ArrayList<>();
        textHistory.add("Hello");
        textHistory.add("error");
        textHistory.add("world");

        // Create ListIterator starting from the end of the list
        ListIterator it = textHistory.________(textHistory.____());

        // Check if more elements available in reserve order
        while (____.____()) {
        	// Retrieve previous element
            String word = ____.____();
            if (word.equals("error")) {
                // Insert "correction" before "error"
                ____.____("correction");
            }
        }

        System.out.println(textHistory);
    }
}

Edit and Run Code