Add dependency on Guava

app/build.gradle

@@ -40,6 +40,7 @@ dependencies {
     compile 'com.journeyapps:zxing-android-embedded:3.2.0@aar'
     compile 'com.google.zxing:core:3.2.1'
     compile 'org.apache.commons:commons-csv:1.2'
+    compile group: 'com.google.guava', name: 'guava', version: '18.0'
     testCompile 'junit:junit:4.12'
     testCompile "org.robolectric:robolectric:3.0"
 }

app/src/main/java/protect/card_locker/MainActivity.java

@@ -123,6 +123,7 @@ public class MainActivity extends AppCompatActivity
         final String[][] USED_LIBRARIES = new String[][]
         {
             new String[] {"Commons CSV", "https://commons.apache.org/proper/commons-csv/"},
+            new String[] {"Guava", "https://github.com/google/guava"},
             new String[] {"ZXing", "https://github.com/zxing/zxing"},
             new String[] {"ZXing Android Embedded", "https://github.com/journeyapps/zxing-android-embedded"},
         };