title: cannot access NPOIFSFileSystem
body: <p>I want to read xls and xlsx files. </p>
  
  <p>I use this line to access my workbook.</p>
  
  <pre><code>myWorkBook = WorkbookFactory.create(file);
  </code></pre>
  
  <p>My build gradle looks like this:
  apply plugin: 'com.android.application'</p>
  
  <pre><code>android {
      compileSdkVersion 19
      buildToolsVersion "19.1.0"
  
      defaultConfig {
          applicationId "com.example.application"
          minSdkVersion 8
          targetSdkVersion 19
          versionCode 1
          versionName "1.0"
      }
      buildTypes {
          release {
              runProguard false
              proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
          }
      }
  
      packagingOptions {
          exclude 'META-INF/DEPENDENCIES.txt'
          exclude 'META-INF/LICENSE.txt'
          exclude 'META-INF/NOTICE.txt'
          exclude 'META-INF/NOTICE'
          exclude 'META-INF/LICENSE'
          exclude 'META-INF/DEPENDENCIES'
          exclude 'META-INF/notice.txt'
          exclude 'META-INF/license.txt'
          exclude 'META-INF/dependencies.txt'
          exclude 'META-INF/LGPL2.1'
      }
  }
  
  dependencies {
      compile fileTree(include: ['*.jar'], dir: 'libs')
      compile 'com.android.support:appcompat-v7:19.1.0'
      compile files('libs/poi-3.7.jar')
      compile files('libs/poi-ooxml-3.9.jar')
      compile project(':aFileChooser')
  }
  </code></pre>
  
  <p>I cannot compile my project as I get the following error:</p>
  
  <blockquote>
    <p>Error:(210, 41) error: cannot access NPOIFSFileSystem
    class file for org.apache.poi.poifs.filesystem.NPOIFSFileSystem not found
    Error:Execution failed for task ':app:compileDebugJava'.
    Compilation failed; see the compiler error output for details.</p>
  </blockquote>
  
  <p>Any ideas what could be wrong?</p>