diff --git a/ch_16/Exercise16_08.java b/ch_16/Exercise16_08.java
new file mode 100644
index 0000000..640ea49
--- /dev/null
+++ b/ch_16/Exercise16_08.java
@@ -0,0 +1,13 @@
+package ch_16;
+
+/**
+ * **16.8 (Geometry: two circles intersect?) Write a program that enables the user to
+ * specify the location and size of the circles and displays whether the two circles
+ * intersect, as shown in Figure 16.39a. Enable the user to point the mouse inside a
+ * circle and drag it. As the circle is being dragged, the circle’s center coordinates
+ * in the text fields are updated.
+ * <p>
+ * FIGURE 16.39 Check whether two circles and two rectangles are overlapping
+ */
+public class Exercise16_08 {
+}
diff --git a/ch_16/exercise16_07/Exercise16_07.java b/ch_16/exercise16_07/Exercise16_07.java
index db67109..04e50c8 100644
--- a/ch_16/exercise16_07/Exercise16_07.java
+++ b/ch_16/exercise16_07/Exercise16_07.java
@@ -2,17 +2,12 @@
 
 import javafx.application.Application;
 import javafx.beans.property.SimpleIntegerProperty;
-import javafx.beans.value.ChangeListener;
-import javafx.beans.value.ObservableValue;
 import javafx.scene.Scene;
 import javafx.scene.control.Label;
 import javafx.scene.control.TextField;
 import javafx.scene.layout.HBox;
 import javafx.scene.layout.Priority;
 import javafx.scene.layout.VBox;
-import javafx.scene.paint.Color;
-import javafx.scene.shape.Circle;
-import javafx.scene.text.TextAlignment;
 import javafx.stage.Stage;
 import javafx.util.converter.NumberStringConverter;
 
diff --git a/ch_23/Exercise23_07.java b/ch_23/Exercise23_07.java
new file mode 100644
index 0000000..ae4bdc0
--- /dev/null
+++ b/ch_23/Exercise23_07.java
@@ -0,0 +1,11 @@
+package ch_23;
+
+/**
+ * 23.7 (Min-heap) The heap presented in the text is also known as a max-heap, in which
+ * each node is greater than or equal to any of its children. A min-heap is a heap
+ * in which each node is less than or equal to any of its children. Min-heaps are
+ * often used to implement priority queues. Revise the Heap class in Listing 23.9 to
+ * implement a min-heap.
+ */
+public class Exercise23_07 {
+}