Installing the anti-compile plugin under eclipse allows you to view the Java source code for the. class file directly.
The anti-compile plugin has jdeclipse and jadeclipse.
(1) jdeclipse
http://www.djjavadecompiler.com/
(2) Jad + jadeclipse
Download Jadeclipse:http://sourceforge.net/projects/jadclipse/files/
Or see my note-taking address:
http://note.youdao.com/yws/public/resource/bd5eb7f827b10534088c7c5085208bbe/355468C26CA948358BF4458CA68A6828
After downloading Net.sf.jadclipse_3.3.0.jar, copy to the plugin folder under the Eclipse home directory and restart Eclipse.
Download Jad.exe:http://www.varaneckas.com/jad/(address found on wiki)
Or see my note-taking address:
http://note.youdao.com/yws/public/resource/bd5eb7f827b10534088c7c5085208bbe/B06333506D5E428787F0FF14B55F5090
after the download is complete, copy to any path, for example, I copy to%java_home%\bin, namely: D:\Program Files\java\jdk1.6.0_33\bin\jad.exe
And then:
Window->preferences->java->jadclipse, in Path to Decompiler , fill in the full pathname of the decompile tool Jad, which is:d:\ Program Files\java\jdk1.6.0_33\bin\jad.exe.
And then:
File associations, Editors, Perference, Windows,
Under File Type, select *.class, and then under associated editors, select the Jadclipse class File Viewer, and click the Default button on the right to set it as the Defaults editor.
  Note, after this setting, you double-click some. class files still cannot decompile, because these class files do not have additional source code, in order to resolve all class files, but also to do the following settings:
Under File type, select *.class without source, (if you don't have an option, you can try clicking the Add button on the right and adding the *.class without source type yourself), and then Associated editors Click on the right Add, add the Jadclipse class file Viewer, then select the Jadclipse class file viewer and click the Default button on the right to Jadclipse The Class File Viewer is set to the default editor for *.class without source .
Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.
Eclipse 4.2 Installing the Java Anti-compilation plugin