[BAEL-3090] Added example

patterns/design-patterns-2/src/main/java/com/baeldung/memento/Coordinates.java

@@ -0,0 +1,12 @@
+package com.baeldung.memento;
+
+public class Coordinates {
+
+    private int x;
+    private int y;
+
+    public Coordinates(int x, int y) {
+        this.x = x;
+        this.y = y;
+    }
+}

patterns/design-patterns-2/src/main/java/com/baeldung/memento/TextEditor.java

@@ -0,0 +1,19 @@
+package com.baeldung.memento;
+
+public class TextEditor {
+
+    private TextWindow textWindow;
+    private TextWindowState savedTextWindow;
+
+    public TextEditor(TextWindow textWindow) {
+        this.textWindow = textWindow;
+    }
+
+    public void hitSave() {
+        savedTextWindow = textWindow.save();
+    }
+
+    public void hitUndo() {
+        textWindow.restore(savedTextWindow);
+    }
+}

patterns/design-patterns-2/src/main/java/com/baeldung/memento/TextWindow.java

@@ -0,0 +1,30 @@
+package com.baeldung.memento;
+
+public class TextWindow {
+
+    private StringBuilder currentText;
+    private Coordinates cursorPosition;
+
+    public TextWindow() {
+        this.currentText = new StringBuilder();
+        this.cursorPosition = new Coordinates(0, 0);
+    }
+
+    public void addText(String text) {
+        currentText.append(text);
+    }
+
+    public TextWindowState save() {
+        return new TextWindowState(currentText.toString());
+    }
+
+    public void restore(TextWindowState save) {
+        currentText = new StringBuilder(save.getText());
+        cursorPosition = atTextEnd();
+    }
+
+    private Coordinates atTextEnd() {
+        String[] lines = currentText.toString().split("\n");
+        return new Coordinates(lines[lines.length - 1].length(), lines.length);
+    }
+}

patterns/design-patterns-2/src/main/java/com/baeldung/memento/TextWindowState.java

@@ -0,0 +1,14 @@
+package com.baeldung.memento;
+
+public class TextWindowState {
+
+    private String text;
+
+    public TextWindowState(String text) {
+        this.text = text;
+    }
+
+    public String getText() {
+        return text;
+    }
+}