Update README.md

jws/src/main/java/com/example/Hello.java

@@ -0,0 +1,15 @@
+package com.example;
+
+import javax.swing.*;
+
+public class Hello {
+    public static void main(String[] args) {
+        JFrame f = new JFrame("main");
+        f.setSize(200, 100);
+        f.setLocationRelativeTo(null);
+        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        JLabel label = new JLabel("Hello, world!");
+        f.add(label);
+        f.setVisible(true);
+    }
+}