[Manan] ADD:Undo/Redo Functionality of Text Editor using a Double Linked List

Author: mananguptamg

TextEditorFunctionality.java

@@ -0,0 +1,130 @@
+// Node class to store each state of the text
+class TextState {
+    String text;
+    TextState next, prev;
+
+    public TextState(String text) {
+        this.text = text;
+        this.next = this.prev = null;
+    }
+}
+
+
+class TextEditorFunctionality {
+    private TextState head, tail, current;
+    private int historyLimit = 10;
+    private int count = 0;
+
+    public TextEditorFunctionality() {
+        head = tail = current = null;
+    }
+
+    // Add a new text state (when user types or performs an action)
+    public void addTextState(String newText) {
+        TextState newState = new TextState(newText);
+
+        // If the list is empty, set as the first state
+        if (head == null) {
+            head = tail = current = newState;
+        } else {
+            // Remove forward history
+            current.next = null;
+            tail = current;
+
+            // Add the new state at the end
+            tail.next = newState;
+            newState.prev = tail;
+            tail = newState;
+            current = newState;
+
+            // If history exceeds the limit, remove the oldest state
+            if (count >= historyLimit) {
+                head = head.next;
+                head.prev = null;
+            } else {
+                count++;
+            }
+        }
+    }
+
+    // Undo: Move to the previous state
+    public void undo() {
+        if (current == null || current.prev == null) {
+            System.out.println("No more undo actions available.");
+            return;
+        }
+        current = current.prev;
+        System.out.println("Undo performed. Current text: " + current.text);
+    }
+
+    // Redo: Move to the next state
+    public void redo() {
+        if (current == null || current.next == null) {
+            System.out.println("No more redo actions available.");
+            return;
+        }
+        current = current.next;
+        System.out.println("Redo performed. Current text: " + current.text);
+    }
+
+    // Display current text state
+    public void displayCurrentText() {
+        if (current == null) {
+            System.out.println("No text available.");
+        } else {
+            System.out.println("Current Text: " + current.text);
+        }
+    }
+
+    public void displayAllStates() {
+        TextState temp = head;
+        if (temp == null) {
+            System.out.println("No history available.");
+            return;
+        }
+        System.out.println("Text History:");
+        while (temp != null) {
+            System.out.println("- " + temp.text);
+            temp = temp.next;
+        }
+    }
+
+    // Main method to test the Undo/Redo functionality
+    public static void main(String[] args) {
+        TextEditorFunctionality editor = new TextEditorFunctionality();
+
+        // Adding text states
+        editor.addTextState("Hello");
+        editor.addTextState("Hello World");
+        editor.addTextState("Hello World! How are you?");
+        editor.addTextState("Hello World! How are you doing today?");
+
+
+        editor.displayCurrentText();
+
+
+        editor.undo();
+        editor.undo();
+
+        editor.redo();
+
+        System.out.println("After Undo and Redo");
+        editor.displayCurrentText();
+
+        // Display all states in the history
+        editor.displayAllStates();
+    }
+}
+
+//SampleOutput
+//Current Text: Hello World! How are you doing today?
+//Undo performed. Current text: Hello World! How are you?
+//Undo performed. Current text: Hello World
+//Redo performed. Current text: Hello World! How are you?
+//After Undo and Redo
+//Current Text: Hello World! How are you?
+//Text History:
+//- Hello
+//- Hello World
+//- Hello World! How are you?
+//- Hello World! How are you doing today?