update:demo3

com/study/demo3/Vehicle.java

@@ -0,0 +1,20 @@
+package com.study.demo3;
+public class Vehicle {
+    protected String name;
+
+    public Vehicle(String name) {
+        this.name = name;
+    }
+    
+    public Vehicle() {
+        this.name = "Unknown Vehicle";
+    }
+
+    public void start() {
+        System.out.println("Vehicle Start");
+    }
+
+    public void stop() {
+        System.out.println("Vehicle Stop");
+    }
+}