instrumentation

Java 8 appears to generate classes to represent lambda expressions. For instance, the code: Runnable r = app::doStuff; Manifests, roughly, as: // $FF: synthetic class final class App$$Lambda$1 implements Runnable { private final App arg$1; private App$$Lambda$1(App var1) { this.arg$1 = var1; } private static Runnable get$Lambda(App var0) { return new App$$Lambda$1(var0); } public void run() { this.arg$1.doStuff(); } } As I understand this, the code is generated at runtime. Now, suppose one wanted to inject code into the run method of the above class. Experiments thus far yield a mix of

I'm trying to add custom behaviour to system classes (FileInputStream/FileOutputStream). I wrote custom ClassFileTransformer with the following transform method: public byte[] transform(ClassLoader arg0, String arg1, Class arg2, ProtectionDomain arg3, byte[] arg4) throws IllegalClassFormatException { System.out.println("class name: " + arg1); return arg4; } When I run sample program: public static void main(String[] args) throws Exception { new FileOutputStream("file"); } I see that no system classes are not passed to transform. Is there any way to modify system classes? Thanks in advance!

I want to write a simple java agent which can print the name of a method called by the java program instrumented. For example, my java program I want to instrument is: public class TestInstr { public static void sayHello() { System.out.println("Hello !"); } public static void main(String args[]) { sayHello(); sayHello(); sayHello(); } } I would like to display something like this : method sayHello has been called Hello ! method sayHello has been called Hello ! method sayHello has been called Hello ! Thanks for your help! You can use an instrumentation library such as Javassist to do that. Let

It seems that the System.Diagnostics.Debug , and System.Diagnostics.Trace are largely the same, with the notable exception that Debug usage is compiled out in a release configuration. When would you use one and not the other? The only answer to this I've dug up so far is just that you use the Debug class to generate output that you only see in debug configuration, and Trace will remain in a release configuration, but that doesn't really answer the question in my head. If you're going to instrument your code, why would you ever use Debug , since Trace can be turned off without a recompile? The