update:demo2

com/study/demo2/Rectangle.java

@@ -0,0 +1,37 @@
+package com.study.demo2;
+
+public class Rectangle {
+    private double width = 1.0;
+    private double height = 1.0;
+
+    public Rectangle() {}
+
+    public Rectangle(double width, double height) {
+        this.width = width;
+        this.height = height;
+    }
+
+    public double getArea() {
+        return width * height;
+    }
+
+    public double getPerimeter() {
+        return 2 * (width + height);
+    }
+
+    public double getWidth() {
+        return width;
+    }
+
+    public void setWidth(double width) {
+        this.width = width;
+    }
+
+    public double getHeight() {
+        return height;
+    }
+
+    public void setHeight(double height) {
+        this.height = height;
+    }
+}