diff --git a/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/ClassConstants.java b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/ClassConstants.java
new file mode 100644
index 0000000000..7fb87b4f1e
--- /dev/null
+++ b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/ClassConstants.java
@@ -0,0 +1,21 @@
+package com.baeldung.compiletimeconstants;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.Arrays;
+import java.util.List;
+
+public class ClassConstants {
+
+    public static final int MAXIMUM_NUMBER_OF_USERS = 10;
+    public static final String DEFAULT_USERNAME = "unknown";
+    public static final List<String> DEFAULT_GROUPS = List.of("all", "reader");
+
+    public static final Logger log = LoggerFactory.getLogger(ClassConstants.class);
+    public static final List<String> contributorGroups = Arrays.asList("contributor", "author");
+
+    public static final int MAXIMUM_NUMBER_OF_GUESTS = MAXIMUM_NUMBER_OF_USERS * 10;
+    public static boolean DEFAULT_GROUPS_DEFINED = DEFAULT_GROUPS != null;
+
+}
\ No newline at end of file
diff --git a/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/CompileTimeVariables.java b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/CompileTimeVariables.java
new file mode 100644
index 0000000000..f9c3231145
--- /dev/null
+++ b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/CompileTimeVariables.java
@@ -0,0 +1,17 @@
+package com.baeldung.compiletimeconstants;
+
+import java.io.PrintWriter;
+
+public class CompileTimeVariables {
+
+    public final int MAXIMUM_LOGIN_ATTEMPTS = 5;
+
+    public static void main(String[] args) {
+        PrintWriter printWriter = System.console().writer();
+        CompileTimeVariables instance = new CompileTimeVariables();
+        final String username = "baeldung";
+        printWriter.println(username);
+        printWriter.println(instance.MAXIMUM_LOGIN_ATTEMPTS);
+    }
+
+}
diff --git a/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/RunTimeVariables.java b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/RunTimeVariables.java
new file mode 100644
index 0000000000..0c801a77a4
--- /dev/null
+++ b/core-java-modules/core-java-lang-4/src/main/java/com/baeldung/compiletimeconstants/RunTimeVariables.java
@@ -0,0 +1,14 @@
+package com.baeldung.compiletimeconstants;
+
+import java.io.Console;
+public class RunTimeVariables {
+
+    public static void main(String[] args) {
+        Console console = System.console();
+        final String input = console.readLine();
+        console.writer().write(input);
+        final double random = Math.random();
+        console.writer().write("Number: " + random);
+    }
+
+}