bytecode

I created a constructor with Javassist which has no real method CtConstructor c = CtNewConstructor.make ( argTypes, null, newClass ); When I'm trying to put out the signature of this class c.getSignature(); I get public Echo ()V I'm confused what "V" means? I expected either public Echo (); or something similar... The JVM uses a compact way of storing method signatures, of which constructors are considered a special case. For your example: () indicates a method taking no arguments V indicates that it returns nothing The other parts of the scheme are: B - byte C - char D - double F - float I -

In Java, does "binary code" means the same as "Java bytecode?" Is this the flow in Java ? Java File (.java) -> [javac] -> ByteCode File (.class) -> [JVM/Java Interpreter] -> Running it(by first converting it into binary code specific to the machine) Thanks! The answer depends on what you mean by binary code . Java bytecode is a binary data format that includes loading information and execution instructions for the Java virtual machine. In that sense, Java bytecode is a special kind of binary code . When you use the term " binary code " to mean machine instructions for a real processors

Often I am stuck with a java class file with no source and I am trying to understand the problem I have at hand. Note a decompiler is useful but not sufficient in all situation... I have two question What tools are available to view java byte code (preferably available from the linux command line ) What are good references to get familiar with java byte code syntax coobird Rather than looking directly at the Java bytecode, which will require familiarity with the Java virtual machine and its operations, one could try to use a Java decompiling utility. A decompiler will attempt to create a java

In a recent question asked recently my simple minded answer highlighted many of my misconceptions about Java, the JVM, and how the code gets compiled and run. This has created a desire in me to take my understanding to a lower level. I have no problems with the low level understanding like assembly how ever bytecode and the JVM confound me. How object oriented code gets broken down on a low level is lost to me. I was wondering if anyone had any suggestion on how to learn about the JVM, bytecode and the lower level functioning of Java. Are there any utilities out there that allow you to write

The design of GHC is based on something called STG, which stands for "spineless, tagless G-machine". Now G-machine is apparently short for "graph reduction machine", which defines how laziness is implemented. Unevaluated thunks are stored as an expression tree, and executing the program involves reducing these down to normal form. (A tree is an acyclic graph, but Haskell's pervasive recursion means that Haskell expressions form general graphs , hence graph-reduction and not tree-reduction.) What is less clear are the terms "spineless" and "tagless". I think that "spineless" refers to the fact

When a java file is compiled, it generates a .class file. Now this .class file has the bytecode which the JVM interprets. when we open the .class file in a text editor, it is not human readable. Now to view the bytecode a disassembler like javap can be used. My question is, why do we need to disassemble bytecode in order to view the bytecode itself? What does the disassembler actually do, to convert the .class file into human readable format? The Java virtual machine simulates a machine. This is why it is called a machine , despite it being a virtual one that does not exist in hardware. Thus,

I have decided to check out Emacs, and I liked it very much. Now, I'm using the Emacs Starter Kit , which sort of provides better defaults and some nice customizations to default install of Emacs. I have customized it a little, added some stuff like yasnippet , color-themes , unbound , and other stuff. I've set up a github repository where I keep all of the customizations so I can access them from multiple places or in case something goes bad and I lose my .emacs.d directory. All of this is very nice, but there is a problem: Emacs takes about 1-2 seconds to load. AFAIK I can compile individual

I started learning Java Agent few days ago. But documentation is not very good and beginners like me struggling to understand the basics. I created a basic multiplier class and export it to runnable jar using eclipse. Here is the code snippet. Main jar file: public class Multiplier { public static void main(String[] args) { int x = 10; int y = 25; int z = x * y; System.out.println("Multiply of x*y = " + z); } } Bytecode for above class Now I want to manipulate the value of x from an agent. I tried to create the Agent class like this Agent: package myagent; import org.objectweb.asm.*; import

Using ASM 5.0.3 (with Java 1.8.0_65 & Tomcat 8.0.30) , Visiting one of the JSP (date.jsp) Method - _JSP(_jspService) , getting below exception javax.servlet.ServletException: java.lang.VerifyError: Operand stack overflow Exception Details: Location: org/apache/jsp/jsp/dates/date_jsp._jspService(Ljavax/servlet/http/HttpServletRequest;Ljavax/servlet/http/HttpServletResponse;)V @0: aload_1 Reason: Exceeded max stack size. Current Frame: bci: @0 flags: { } locals: { 'org/apache/jsp/jsp/dates/date_jsp', 'javax/servlet/http/HttpServletRequest', 'javax/servlet/http/HttpServletResponse' } stack: { }

I've this java source file: import java.util.function.*; public class t { public static void main(String[] args) { Function<Integer,Integer> r = (a) -> a*a+2*a+1; System.out.println(r.apply(2)); } } I compile it and it works as expected. Here 's the output of javap -c -v t , and I can't find the location of lambda in it. Where's the bytecode which tells the jvm to compute the expression with the input Integer whenever the lambda is envoked? If you want to see the code of your lambda body a*a+2*a+1 , you should call javap -c -v -p t to see also the private methods: private static java.lang