Mini articles/java unknown stack trace (#11627)

* unknown source in stack trace

* Improved comment

* creating an intentional exception

Co-authored-by: Sameer <d7495b5879fca1ec1367476a5395a60a8e9baec9>

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/unknownsourcestacktrace/Main.java

@@ -0,0 +1,25 @@
+package com.baeldung.unknownsourcestacktrace;
+
+import com.baeldung.unknownsourcestacktrace.dto.User;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public class Main {
+    private static final Logger logger = LoggerFactory.getLogger(Main.class);
+    private static final int SHORT_NAME_LIMIT = 10;
+
+    public static void main(String[] args) {
+        User user = new User();
+        user.setName("Tom");
+
+        logger.info(getGreetingMessage(user.getName()));
+    }
+
+    private static String getGreetingMessage(String name) {
+        return "Welcome " + getShortenedName(name) + "!";
+    }
+
+    private static String getShortenedName(String name) {
+        return name.substring(0, SHORT_NAME_LIMIT);
+    }
+}

core-java-modules/core-java-exceptions-3/src/main/java/com/baeldung/unknownsourcestacktrace/dto/User.java

@@ -0,0 +1,13 @@
+package com.baeldung.unknownsourcestacktrace.dto;
+
+public class User {
+    private String name;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}