Node.setData(): add ability to change node's data after instantiation

src/main/java/net/kemitix/node/Node.java

@@ -34,6 +34,13 @@ public interface Node<T> {
      */
     T getData();
 
+    /**
+     * Set the data held within the node.
+     *
+     * @param data the node's data
+     */
+    void setData(T data);
+
     /**
      * Returns true if the node is empty (has no data).
      *

src/main/java/net/kemitix/node/NodeItem.java

@@ -16,7 +16,7 @@ import java.util.function.Function;
  */
 public class NodeItem<T> implements Node<T> {
 
-    private final T data;
+    private T data;
 
     private final Set<Node<T>> children = new HashSet<>();
 
@@ -127,6 +127,11 @@ public class NodeItem<T> implements Node<T> {
         return data;
     }
 
+    @Override
+    public void setData(final T data) {
+        this.data = data;
+    }
+
     @Override
     public boolean isEmpty() {
         return data == null;

src/test/java/net/kemitix/node/NodeItemTest.java

@@ -878,4 +878,14 @@ public class NodeItemTest {
                 "[  lucy]");
         assertThat(lines).containsSubsequence("[root]", "[ bob]");
     }
+
+    @Test
+    public void canChangeNodeData() {
+        //given
+        node = new NodeItem<>("initial");
+        //when
+        node.setData("updated");
+        //then
+        assertThat(node.getData()).isEqualTo("updated");
+    }
 }