title: Java Incompatible magic value 4022320623
body: <p>Im getting a strange error when im compiling my code on a server and downloading it and trying to run it on my computer.</p>
  
  <p>Im basically compiling some java files on an EC2 instance, then loading them into a storage for later use.</p>
  
  <p>When i download the files onto my computer and try to run them i am getting the following errors:</p>
  
  <pre><code>Exception in thread "main" java.lang.ClassFormatError: Incompatible magic value  
       4022320623 in class file HelloWorldPackage/HelloWorldClass
      at java.lang.ClassLoader.defineClass1(Native Method)
      at java.lang.ClassLoader.defineClass(ClassLoader.java:787)
      at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
      at java.net.URLClassLoader.defineClass(URLClassLoader.java:447)
  at java.net.URLClassLoader.access$100(URLClassLoader.java:71)
  at java.net.URLClassLoader$1.run(URLClassLoader.java:361)
  at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
  at java.security.AccessController.doPrivileged(Native Method)
  at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:423)
  at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
  at java.lang.ClassLoader.loadClass(ClassLoader.java:356)
  at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:476)
  </code></pre>
  
  <p>I am compiling the files using the following method:</p>
  
  <pre><code>public void compileProject()
  {
  
  
      String command = "javac ";
      for(String s: this.getPackages())
      {
          File[] files = new File("/home/benuni/CompileFiles/" + project + "/src/" + s).listFiles(new FilenameFilter() {
              public boolean accept(File dir, String name) {
                  return name.endsWith(".java");
              }
          });
  
          for(File f: files)
          {
              command = command + f.getAbsolutePath() + " ";
          }
      }
  
      try {
          System.out.println("command: '"+ command +"'");
          Process pro = Runtime.getRuntime().exec(command);
           printLines(" stderr:", pro.getErrorStream());
  
          pro.waitFor();
  
          this.moveClassFiles();
      } catch (IOException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      } catch (InterruptedException e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      } catch (Exception e) {
          // TODO Auto-generated catch block
          e.printStackTrace();
      }
  
  
  }
  </code></pre>
  
  <p>and am uploading the files with this method:</p>
  
  <pre><code>public void uploadBin()
  {
      for(String s: this.getPackages())
      {
          File[] filesInPackage = new File("/home/benuni/CompileFiles/"+this.project+"/bin/"+s).listFiles();
  
          for(File f: filesInPackage)
          {
              String key = this.project+"/"+this.version+"/bin/"+s+"/"+f.getName();
              s3.putObject("devcloud",key,f);
  
          }
  
      }
  
  }
  </code></pre>
  
  <p>does anyone know what i am doing wrong?
  The class files are runnable when i compile them on the computer, but when i upload them to the cloud and download them im getting the error?</p>
  
  <p>Thanks,</p>
  
  <p>Ben</p>