Extracted ChangeManager interface from concrete implementation

src/main/java/dev/kske/undoredo/ChangeManager.java

@@ -1,6 +1,6 @@
 package dev.kske.undoredo;
 
-import java.util.*;
+import java.util.List;
 
 /**
  * A change manager keeps track of subsequent changes and allows un- and redoing them. A specific
@@ -9,14 +9,10 @@ import java.util.*;
  *
  * @param <C> the change type to store in this change manager
  * @author Maximilian K&auml;fer
+ * @author Kai S. K. Engelbart
  * @since 0.0.1
  */
-public final class ChangeManager<C extends Change> {
+public interface ChangeManager<C extends Change> {
-
-	private final List<C> changes = new LinkedList<>();
-
-	private int	index		= -1;
-	private int	markedIndex	= -1;
 
 	/**
 	 * Applies the given change and appends it to the change list.
@@ -24,11 +20,7 @@ public final class ChangeManager<C extends Change> {
 	 * @param change the change to add
 	 * @since 0.0.1
 	 */
-	public void addChange(C change) {
+	void addChange(C change);
-		change.apply();
-		changes.add(change);
-		++index;
-	}
 
 	/**
 	 * Undoes the current change.
@@ -36,14 +28,7 @@ public final class ChangeManager<C extends Change> {
 	 * @return whether an action was performed
 	 * @since 0.1.0
 	 */
-	public boolean undo() {
+	boolean undo();
-		if (isUndoAvailable()) {
-			changes.get(index).invert().apply();
-			--index;
-			return true;
-		}
-		return false;
-	}
 
 	/**
 	 * Applies the change that was undone before.
@@ -51,47 +36,32 @@ public final class ChangeManager<C extends Change> {
 	 * @return whether an action was performed
 	 * @since 0.0.1
 	 */
-	public boolean redo() {
+	boolean redo();
-		if (isRedoAvailable()) {
-			changes.get(index + 1).apply();
-			++index;
-			return true;
-		}
-		return false;
-	}
 
 	/**
 	 * Marks the current change.
 	 *
 	 * @since 0.0.1
 	 */
-	public void mark() {
+	void mark();
-		markedIndex = index;
-	}
 
 	/**
 	 * @return whether the current change is marked
 	 * @since 0.0.1
 	 */
-	public boolean isAtMarkedIndex() {
+	boolean isAtMarkedIndex();
-		return markedIndex == index;
-	}
 
 	/**
 	 * @return whether a change is present that can be undone
 	 * @since 0.0.1
 	 */
-	public boolean isUndoAvailable() {
+	boolean isUndoAvailable();
-		return index > -1;
-	}
 
 	/**
 	 * @return whether a change is present that can be redone
 	 * @since 0.0.1
 	 */
-	public boolean isRedoAvailable() {
+	boolean isRedoAvailable();
-		return index < changes.size() - 1;
-	}
 
 	/**
 	 * Provides an unmodifiable view of the changes stored in this change manager.
@@ -99,7 +69,5 @@ public final class ChangeManager<C extends Change> {
 	 * @return all stored changes
 	 * @since 0.0.1
 	 */
-	public List<C> getChanges() {
+	List<C> getChanges();
-		return Collections.unmodifiableList(changes);
-	}
 }

src/main/java/dev/kske/undoredo/UnlimitedChangeManager.java

@@ -0,0 +1,69 @@
+package dev.kske.undoredo;
+
+import java.util.*;
+
+/**
+ * @param <C> the change type to store in this change manager
+ * @author Maximilian K&auml;fer
+ * @author Kai S. K. Engelbart
+ * @since 0.0.1
+ */
+public final class UnlimitedChangeManager<C extends Change> implements ChangeManager<C> {
+
+	private final List<C> changes = new LinkedList<>();
+
+	private int	index		= -1;
+	private int	markedIndex	= -1;
+
+	@Override
+	public void addChange(C change) {
+		change.apply();
+		changes.add(change);
+		++index;
+	}
+
+	@Override
+	public boolean undo() {
+		if (isUndoAvailable()) {
+			changes.get(index).invert().apply();
+			--index;
+			return true;
+		}
+		return false;
+	}
+
+	@Override
+	public boolean redo() {
+		if (isRedoAvailable()) {
+			changes.get(index + 1).apply();
+			++index;
+			return true;
+		}
+		return false;
+	}
+
+	@Override
+	public void mark() {
+		markedIndex = index;
+	}
+
+	@Override
+	public boolean isAtMarkedIndex() {
+		return markedIndex == index;
+	}
+
+	@Override
+	public boolean isUndoAvailable() {
+		return index > -1;
+	}
+
+	@Override
+	public boolean isRedoAvailable() {
+		return index < changes.size() - 1;
+	}
+
+	@Override
+	public List<C> getChanges() {
+		return Collections.unmodifiableList(changes);
+	}
+}

src/test/java/dev/kske/undoredo/ChangeManagerTest.java

@@ -16,7 +16,7 @@ class ChangeManagerTest {
 
 	@BeforeEach
 	void prepareChangeManager() {
-		manager	= new ChangeManager<>();
+		manager	= new UnlimitedChangeManager<>();
 		wrapper	= new IntWrapper();
 		change	= new IntChange(wrapper, 1);
 	}