用户管理高级版

src/chapter4/Example25.java

@@ -0,0 +1,4 @@
+package chapter4;
+
+public class Examaple25 {
+}

src/chapter4/demo45/Main.java

@@ -16,7 +16,8 @@ public class Main {
                 case 1: // 圆形
                     System.out.print("请输入圆形的半径：");
                     double radius = sc.nextDouble();
-                    Shape circle = new Circle(radius);
+                    Circle circle = new Circle(radius);
+//                    Shape circle = new Circle(radius);
                     ShapeCalculate.printArea(circle);
                     ShapeCalculate.printPerimeter(circle);
                     break;
@@ -24,7 +25,8 @@ public class Main {
                     System.out.print("请输入长方形的长和宽：");
                     double length = sc.nextDouble();
                     double width = sc.nextDouble();
-                    Shape rectangle = new Rectangle(length, width);
+//                    Shape rectangle = new Rectangle(length, width);
+                    Rectangle rectangle = new Rectangle(length, width);
                     ShapeCalculate.printArea(rectangle);
                     ShapeCalculate.printPerimeter(rectangle);
                     break;

src/chapter4/demo45/ShapeCalculate.java

@@ -13,12 +13,33 @@ public final class ShapeCalculate {
 
     // 打印图形面积
     public static void printArea(Shape shape) {
-        System.out.println("面积："+shape.getArea());
+        if (shape instanceof Rectangle) {
+            System.out.println("正方形面积："+shape.getArea());
+        } else if (shape instanceof Circle) {
+            System.out.println("圆形面积："+shape.getArea());
+        } else {
+            System.out.println("未知图形面积：" + shape.getArea());
+        }
     }
 
     // 打印图形周长
-    public static void printPerimeter(Shape shape) {
-        System.out.println("周长："+shape.getPerimeter());
+//    public static void printPerimeter(Shape shape) {
+//        if (shape instanceof Rectangle) {
+//            System.out.print("长方形");
+//        } else if (shape instanceof Circle) {
+//            System.out.print("圆形");
+//        } else {
+//            System.out.print("未知图形");
+//        }
+//        System.out.println("周长："+shape.getPerimeter());
+//    }
+
+    public static void printPerimeter(Circle circle) {
+        System.out.println("圆形周长："+circle.getPerimeter());
+    }
+
+    public static void printPerimeter(Rectangle rectangle) {
+        System.out.println("长方形周长："+rectangle.getPerimeter());
     }
 
     // 打印计算器菜单

src/chapter4/example14/Example14.java

@@ -0,0 +1,2 @@
+package chapter4.example14;public class Example14 {
+}

src/chapter4/object/Test.java

@@ -0,0 +1,19 @@
+package chapter4.object;
+
+class Student {
+    private String name;
+    private int age;
+
+    public Student(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String toString() {
+        return "Student {name=" + name + ", age=" + age + "}";
+    }
+}
+
+public class Test {
+
+}