title: Bad class file magic or version
body: <p>I already know that question has been already asked very often and answers, but no one of the answers i found fixed my problem.</p>
  
  <p>It's the error:</p>
  
  <pre><code>Error:Gradle: Execution failed for task ':ffcommunity:preDexDebug'.
   com.android.ide.common.internal.LoggedErrorException: Failed to run command:
      D:\Android SDK\sdk\build-tools\20.0.0\dx.bat --dex --output D:\Users\ReVo\Documents\IntelliJ IDEA\FFCommunity\ffcommunity\build\intermediates\pre-dexed\debug\bananaquery-2ee85432877a057e7414910b8127805535139d5d.jar D:\Users\ReVo\Documents\IntelliJ IDEA\FFCommunity\ffcommunity\libs\bananaquery.jar
  Error Code:
      1
  Output:
      UNEXPECTED TOP-LEVEL EXCEPTION:
      com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000)
          at com.android.dx.cf.direct.DirectClassFile.parse0(DirectClassFile.java:472)
          at com.android.dx.cf.direct.DirectClassFile.parse(DirectClassFile.java:406)
          at com.android.dx.cf.direct.DirectClassFile.parseToInterfacesIfNecessary(DirectClassFile.java:388)
          at com.android.dx.cf.direct.DirectClassFile.getMagic(DirectClassFile.java:251)
          at com.android.dx.command.dexer.Main.processClass(Main.java:665)
          at com.android.dx.command.dexer.Main.processFileBytes(Main.java:634)
          at com.android.dx.command.dexer.Main.access$600(Main.java:78)
          at com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:572)
          at com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284)
          at com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166)
          at com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144)
          at com.android.dx.command.dexer.Main.processOne(Main.java:596)
          at com.android.dx.command.dexer.Main.processAllFiles(Main.java:498)
          at com.android.dx.command.dexer.Main.runMonoDex(Main.java:264)
          at com.android.dx.command.dexer.Main.run(Main.java:230)
          at com.android.dx.command.dexer.Main.main(Main.java:199)
          at com.android.dx.command.Main.main(Main.java:103)
      ...while parsing com/comuf/revonline/bananaquery/BananaInsert.class
      1 error; aborting
  </code></pre>
  
  <p>The error is <code>bad class file magic (cafebabe) or version (0034.0000)</code>.</p>
  
  <p>I builded and execute the application without problems many times in the same day but now this fails everytime with this message.</p>
  
  <hr>
  
  <p>Project SDK is <code>Android API 19 Platform</code> and project level is <code>1.7</code>.</p>
  
  <p>CompileSDK is <code>19</code> and buildToolsVersion is <code>'20.0.0'</code>.</p>
  
  <p>Compile options:</p>
  
  <pre><code>compileOptions {
      sourceCompatibility JavaVersion.VERSION_1_7
      targetCompatibility JavaVersion.VERSION_1_7
  }
  </code></pre>
  
  <p>and in <code>dependencies</code> i have:</p>
  
  <pre><code>compile files('libs/bananaquery.jar')
  </code></pre>
  
  <hr>
  
  <p>The library is build with SDK <code>Android API 19 Platform</code> with project level <code>1.7</code>.</p>
  
  <p>My <code>.jar</code> file is inside <code>libs/</code> folder.</p>
  
  <p>I use IntelliJ IDEA 14 Preview, it could be the reason? With IntellIJ IDEA 13 it remains stuck at "Gradle sync"</p>
  
  <p><em>compile files could be useless since i have <code>compile fileTree(dir: 'libs', include: ['*.jar'])</code> too</em></p>