Update CH08.md

fix typo & parameter data type

Author: JeffChern

docs/CH08.md

@@ -643,7 +643,7 @@ public class CloneDemo {
 
     public class ConcreteCircle {
         private double radius;
-        public void setRedius(int radius) { this.radius = radius; }
+        public void setRadius(double radius) { this.radius = radius; }
         public double getRadius() { return radius; }
         public void render() {
             System.out.printf("畫一個半徑 %f 的實心圓\n", getRadius());
@@ -652,7 +652,7 @@ public class CloneDemo {
 
     public class HollowCircle {
         private double radius;
-        public void setRedius(int radius) { this.radius = radius; }
+        public void setRadius(double radius) { this.radius = radius; }
         public double getRadius() { return radius; }
         public void render() {
             System.out.printf("畫一個半徑 %f 的空心圓\n", getRadius());
@@ -666,7 +666,7 @@ public class CloneDemo {
 public abstract class AbstractCircle {
     protected double radius;
 
-    public void setRedius(int radius) { this.radius = radius; }
+    public void setRadius(double radius) { this.radius = radius; }
     public double getRadius() { return radius; }
 
     public abstract void render();