图形

w5/Main.java → w4/Main.java

@@ -1,9 +1,9 @@
 public class Main {
     public static void main(String[] args) {
         // 创建图形对象
-        Shape circle = new Circle(3);
-        Shape rectangle = new Rectangle(4, 5);
-        Shape triangle = new Triangle(6, 8);
+        Shape circle = new Circle(6);
+        Shape rectangle = new Rectangle(7, 9);
+        Shape triangle = new Triangle(7, 10);
 
         // 统一计算并打印面积
         ShapeUtil.printArea(circle);

w5/Shape.java → w4/Shape.java

@@ -1,17 +1,17 @@
 
-    abstract class Shape {
-        public abstract double getArea();
+    abstract class Shape {//定义一个抽象类
+        public abstract double getArea();//强制所有图形都必须能计算面积
     }
 
     // 圆形
-    class Circle extends Shape {
-        private double radius;
+    class Circle extends Shape {//继承shape，必须实现getarea
+        private double radius;//半径私有属性
 
         public Circle(double radius) {
             this.radius = radius;
-        }
+        }//构造方法无返回值，给对象赋初始值
 
-        @Override
+        @Override//重写父类方法
         public double getArea() {
             return Math.PI * radius * radius;
         }
@@ -50,8 +50,8 @@
     }
 
     // 工具类
-    class ShapeUtil {
-        public static void printArea(Shape shape) {
+    class ShapeUtil {//专门用来打印图形面积
+        public static void printArea(Shape shape) {//任意接受一个图形
             System.out.println("图形面积：" + shape.getArea());
         }
     }