Q:

DexException: Multiple dex files

Okay so currently i am making an Android app that utilizes the Google Sheets API version 3.0 and Drive API Client Library for Java, i need the app to read a spreadhsheet from a users drive account and edit it. Following the documentation i have included the following jars in my /lib folder(Android Studio 1.1).dependencies {
    compile fileTree(include: ['*.jar'], dir: 'libs')
    compile 'com.android.support:appcompat-v7:21.0.3'
    compile 'com.google.android.gms:play-services:6.5.87'
    compile files('libs/google-api-client-1.19.1.jar')
    compile files('libs/google-api-client-android-1.19.1.jar')
    compile files('libs/google-api-services-drive-v2-rev158-1.19.1.jar')
    compile files('libs/google-http-client-1.19.0.jar')
    compile files('libs/google-http-client-android-1.19.0.jar')
    compile files('libs/google-http-client-gson-1.19.0.jar')
    compile files('libs/google-oauth-client-1.19.0.jar')
    compile files('libs/gson-2.1.jar')
    compile files('libs/jackson-core-2.1.3.jar')
    compile files('libs/jackson-core-asl-1.9.11.jar')
    compile files('libs/jsr305-1.3.9.jar')
    compile files('libs/protobuf-java-2.4.1.jar')
    compile files('libs/mail.jar')
    compile files('libs/jsr305.jar')
    compile files('libs/guava-11.0.2.jar')
    compile files('libs/gdata-spreadsheet-meta-3.0.jar')
    compile files('libs/gdata-spreadsheet-3.0.jar')
    compile files('libs/gdata-docs-meta-3.0.jar')
    compile files('libs/gdata-docs-3.0.jar')
    compile files('libs/gdata-core-1.0.jar')
    compile files('libs/gdata-client-meta-1.0.jar')
    compile files('libs/gdata-client-1.0.jar')
    compile files('libs/additionnal.jar')
    compile files('libs/activation.jar')
}When im typing my code everything works just fine, everything is imported appropiately but when i run my app i get this result.
`What went wrong:
Execution failed for task ':app:dexDebug'.
> com.android.ide.common.internal.LoggedErrorException: Failed to run command:
    C:\Users\Ricardo\AppData\Local\Android\sdk\build-tools\21.1.2\dx.bat --dex --output C:\Users\Ricardo\Google Drive\Development\Android\Updated\Private\Google_Fiasco\MyApplication\app\build\intermediates\dex\debug --input-list=C:\Users\Ricardo\Google Drive\Development\Android\Updated\Private\Google_Fiasco\MyApplication\app\build\intermediates\tmp\dex\debug\inputList.txt
Error Code:
    2
Output:

    UNEXPECTED TOP-LEVEL EXCEPTION:
    com.android.dex.DexException: Multiple dex files define Ljavax/annotation/CheckForNull;
        at com.android.dx.merge.DexMerger.readSortableTypes(DexMerger.java:596)
        at com.android.dx.merge.DexMerger.getSortedTypes(DexMerger.java:554)
        at com.android.dx.merge.DexMerger.mergeClassDefs(DexMerger.java:535)
        at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:171)
        at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
        at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
        at com.android.dx.command.dexer.Main.runMonoDex(Main.java:303)
        at com.android.dx.command.dexer.Main.run(Main.java:246)
        at com.android.dx.command.dexer.Main.main(Main.java:215)
        at com.android.dx.command.Main.main(Main.java:106)
e`<br>

Now a couple things to note, when i make two separate projects ,one implementing the Spreadsheet API and the other the Drive API no errors occur. The error only occurs when i implement both API's in the same project i.e combining the jars from both libraries. After tinkering with the jars i found that the error only happens when both jsr305.jar & jsr305-1.3.9.jar are included. Looking at these two jars i see that both have CheckForNull.java files, the file referenced in the error message Multiple dex files define Ljavax/annotation/CheckForNull.
So my question: How do i resolve this error? I think i have to exclude it in my dependencies? Precise instructions would be appreciated, and perhaps an explanation on what the solution does. Also one last thing What difference does it make between simply putting jar files in my /lib folder and adding it to my dependencies in build.gradle? It doesn't seem to affect anything.
The result of deleting either of the jsr.jat files is the following: UNEXPECTED TOP-LEVEL EXCEPTION:
    com.android.dex.DexIndexOverflowException: method ID not in [0, 0xffff]: 65536
        at com.android.dx.merge.DexMerger$6.updateIndex(DexMerger.java:502)
        at com.android.dx.merge.DexMerger$IdMerger.mergeSorted(DexMerger.java:277)
        at com.android.dx.merge.DexMerger.mergeMethodIds(DexMerger.java:491)
        at com.android.dx.merge.DexMerger.mergeDexes(DexMerger.java:168)
        at com.android.dx.merge.DexMerger.merge(DexMerger.java:189)
        at com.android.dx.command.dexer.Main.mergeLibraryDexBuffers(Main.java:454)
        at com.android.dx.command.dexer.Main.runMonoDex(Main.java:303)
        at com.android.dx.command.dexer.Main.run(Main.java:246)
        at com.android.dx.command.dexer.Main.main(Main.java:215)
        at com.android.dx.command.Main.main(Main.java:106)

A:

This error is caused by having too many method referenced in your project. You can read more here. 
Generally it means that you need to remove unused libraries or use proguard even on debug build to reduce the number of method referenced. You may also go with the multi-dex approached mentioned in the article but it makes your project more complicated.

