add a simple program under java_playground

fishercoder1534 · fishercoder1534 · commit c664f91c85c1 · 2024-01-23T11:25:20.000-08:00
diff --git a/src/main/java/java_playground/MainApp.java b/src/main/java/java_playground/MainApp.java
@@ -0,0 +1,8 @@
+package java_playground;
+
+public class MainApp {
+    public static void main(String... args) {
+        System.out.println("Hello world.");
+        System.out.println("Program finished.");
+    }
+}
