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Java: Check Class Version

Here is a simple piece of code to check your Java class version, whether is it is compiled with JDK 4, JDK 5 or JDK 6, etc…

   1: try {
   2:          String filename = "C:\\MyClass.class";
   3:          DataInputStream in = new DataInputStream
   4:                  (new FileInputStream(filename));
   5:  
   6:          int magic = in.readInt();
   7:          if (magic != 0xcafebabe) {
   8:              log.info(filename + " is not a valid class!");
   9:          }
  10:          int minor = in.readUnsignedShort();
  11:          int major = in.readUnsignedShort();
  12:          log.info(filename + ": " + major + " . " + minor);
  13:          in.close();
  14:      } catch (IOException e) {
  15:          log.info("Exception: " + e.getMessage(), e);
  16:      }

major  minor Java platform version
45         3           1.0
45         3           1.1
46         0           1.2
47         0           1.3
48         0           1.4
49         0           1.5
50         0           1.6


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