Android Studio preDexDebug After Adding jar File

Question

I have a framework of my own that I use for in-class tasks (school class, not Java class), and I made it into a .jar file so that whenever I make changes to the framework, I can just drag and drop it into Android Studio. Everything worked well for the past 5 or so class tasks, and now all of a sudden I'm getting a preDexDebug failed error when parsing my .jar after clicking run. I tested this on a blank project. The project has a total of 2 .jars: Gson, and my own jar. It prints out preDexDebug failed right after I pull in my own .jar... I've wrestled with this for two infuriating hours, and I don't know what I can do to fix this at all...

I've tried rebuilding, cleaning, checking gradle.build for duplicates, replicating the project multiple times, and also compiling and copying the .jar multiple times as well.

Ubuntu x64 with 64 bit Oracle JDK 1.8.0_31. Using Java bundled with the JDK

Android Studio output:

Configuration on demand is an incubating feature.
:app:preBuild UP-TO-DATE
:app:preDebugBuild UP-TO-DATE
:app:compileDebugNdk UP-TO-DATE
:app:checkDebugManifest
:app:preReleaseBuild UP-TO-DATE
:app:prepareComAndroidSupportAppcompatV72103Library UP-TO-DATE
:app:prepareComAndroidSupportSupportV42103Library UP-TO-DATE
:app:prepareDebugDependencies
:app:compileDebugAidl UP-TO-DATE
:app:compileDebugRenderscript UP-TO-DATE
:app:generateDebugBuildConfig UP-TO-DATE
:app:generateDebugAssets UP-TO-DATE
:app:mergeDebugAssets UP-TO-DATE
:app:generateDebugResValues UP-TO-DATE
:app:generateDebugResources UP-TO-DATE
:app:mergeDebugResources UP-TO-DATE
:app:processDebugManifest UP-TO-DATE
:app:processDebugResources UP-TO-DATE
:app:generateDebugSources UP-TO-DATE
:app:compileDebugJava
:app:preDexDebug
AGPBI: {"kind":"SIMPLE","text":"UNEXPECTED TOP-LEVEL EXCEPTION:","position":{},"original":"UNEXPECTED TOP-LEVEL EXCEPTION:"}
AGPBI: {"kind":"SIMPLE","text":"com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000)","position":{},"original":"com.android.dx.cf.iface.ParseException: bad class file magic (cafebabe) or version (0034.0000)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.DirectClassFile.parse0(DirectClassFile.java:472)","position":{},"original":"\tat com.android.dx.cf.direct.DirectClassFile.parse0(DirectClassFile.java:472)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.DirectClassFile.parse(DirectClassFile.java:406)","position":{},"original":"\tat com.android.dx.cf.direct.DirectClassFile.parse(DirectClassFile.java:406)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.DirectClassFile.parseToInterfacesIfNecessary(DirectClassFile.java:388)","position":{},"original":"\tat com.android.dx.cf.direct.DirectClassFile.parseToInterfacesIfNecessary(DirectClassFile.java:388)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.DirectClassFile.getMagic(DirectClassFile.java:251)","position":{},"original":"\tat com.android.dx.cf.direct.DirectClassFile.getMagic(DirectClassFile.java:251)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.processClass(Main.java:704)","position":{},"original":"\tat com.android.dx.command.dexer.Main.processClass(Main.java:704)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.processFileBytes(Main.java:673)","position":{},"original":"\tat com.android.dx.command.dexer.Main.processFileBytes(Main.java:673)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.access$300(Main.java:83)","position":{},"original":"\tat com.android.dx.command.dexer.Main.access$300(Main.java:83)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:602)","position":{},"original":"\tat com.android.dx.command.dexer.Main$1.processFileBytes(Main.java:602)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284)","position":{},"original":"\tat com.android.dx.cf.direct.ClassPathOpener.processArchive(ClassPathOpener.java:284)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166)","position":{},"original":"\tat com.android.dx.cf.direct.ClassPathOpener.processOne(ClassPathOpener.java:166)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144)","position":{},"original":"\tat com.android.dx.cf.direct.ClassPathOpener.process(ClassPathOpener.java:144)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.processOne(Main.java:632)","position":{},"original":"\tat com.android.dx.command.dexer.Main.processOne(Main.java:632)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.processAllFiles(Main.java:510)","position":{},"original":"\tat com.android.dx.command.dexer.Main.processAllFiles(Main.java:510)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.runMonoDex(Main.java:280)","position":{},"original":"\tat com.android.dx.command.dexer.Main.runMonoDex(Main.java:280)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.run(Main.java:246)","position":{},"original":"\tat com.android.dx.command.dexer.Main.run(Main.java:246)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.dexer.Main.main(Main.java:215)","position":{},"original":"\tat com.android.dx.command.dexer.Main.main(Main.java:215)"}
AGPBI: {"kind":"SIMPLE","text":"\tat com.android.dx.command.Main.main(Main.java:106)","position":{},"original":"\tat com.android.dx.command.Main.main(Main.java:106)"}
AGPBI: {"kind":"SIMPLE","text":"...while parsing reactor/communications/ClientEndpointTCP.class","position":{},"original":"...while parsing reactor/communications/ClientEndpointTCP.class"}
AGPBI: {"kind":"SIMPLE","text":"1 error; aborting","position":{},"original":"1 error; aborting"}

Answer 1

Turns out Java 8 is not yet supported by the Android SDK (Or something along those lines). Installing Oracle JDK 7 on my desktop, and recompiling my .jar fixed the issue completely.

The most important part was in the second line of the error produced: "bad class file magic (cafebabe) or version (0034.0000)". 0x34 is hex for 52, which means that the binaries are targeted for JREs that support Java 8, but Android Studio's system requirements state that JDK 7 is required

Steps to switch to Oracle JDK 7:

1. Download JDK .tar from Oracle's site
2. Untar contents to /opt/
3. sudo update-alternatives --install /bin/java java /opt/jdk*version*/jre/bin/java 1023
4. sudo update-alternatives --install /bin/javac javac /opt/jdk*version*/bin/javac 1023
5. sudo update-alternatives --install /bin/jar jar /opt/jdk*version*/bin/jar 1023

https://askubuntu.com/questions/56104/how-can-i-install-sun-oracles-proprietary-java-jdk-6-7-8-or-jre