The only reason to convert a .class file to a .java file would be to attempt to reverse engineer a piece of Java code. Disadvantages of this would include near-incomprehensible code being produced by the reverse engineering program.
Java source files have the .java extension, compiled Java class files have the .class extension.
.class is the extension of a java byte code file.
A class file is a compiled .java file and cannot be executed without jdk or java. They are often executed with .bat files in windows for convenience
Java compiler available on multiple platforms, the class files it generates are platform-independent.
Java does not require header files like C/C++.
You need a decompiler to convert class files to java source files. JAD is a Java Decompiler that can do it for you.
Java source files have the .java extension, compiled Java class files have the .class extension.
.class is the extension of a java byte code file.
"class" files are compiled Java files. Perhaps they are meant to be run with Java. It is possible that the download file has other types of downloads available, but I didn't check this.
wrapper class is a predefined class .it is used for converting primitive data types into object type
A class file is a compiled .java file and cannot be executed without jdk or java. They are often executed with .bat files in windows for convenience
The Java Servlet is like every other Java class. You can compile it using the javac command or if you are using a Integrated Development Environment (IDE) like Eclipse, it will compile the class for you. One main difference w.r.t Servlets is the fact that, they get deployed into EAR files (Enterprise Archive Files) and not JAR files (Java Archive Files) like normal java apps.
Java compiler available on multiple platforms, the class files it generates are platform-independent.
I use JD-GUI to de-compile class files back into their java equivalents. This has saved me once or twice when I lost the source code on a project and I needed to update it.
An applet is a Java application, this saves files in a .class extension
Java does not require header files like C/C++.
The class/jar was compiled with a later major version of java than the version of java you are using to run the code with. So for instance the class was compiled with java 1.5 and you are running the class with java 1.4, which doesn't understand the format of 1.5 class files. check "java -version" from the command prompt.