Added the Java Agent Example

core-java-modules/core-java-jvm-2/src/test/java/com/baeldung/objectsize/InstrumentedSize.java

@@ -0,0 +1,11 @@
+package com.baeldung.objectsize;
+
+public class InstrumentedSize {
+
+    public static void main(String[] args) {
+        String ds = "Data Structures";
+        Course course = new Course(ds);
+
+        System.out.println(ObjectSizeCalculator.sizeOf(course));
+    }
+}

core-java-modules/core-java-jvm-2/src/test/java/com/baeldung/objectsize/MANIFEST.MF

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+Premain-Class: com.baeldung.objectsize.ObjectSizeCalculator

core-java-modules/core-java-jvm-2/src/test/java/com/baeldung/objectsize/ObjectSizeCalculator.java

@@ -0,0 +1,16 @@
+package com.baeldung.objectsize;
+
+import java.lang.instrument.Instrumentation;
+
+public class ObjectSizeCalculator {
+
+    private static Instrumentation instrumentation;
+
+    public static void premain(String args, Instrumentation inst) {
+        instrumentation = inst;
+    }
+
+    public static long sizeOf(Object o) {
+        return instrumentation.getObjectSize(o);
+    }
+}