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Hello all! I have been trying to deploy code to this year's robot but have been receiving an error when I attempt to do so. The compiler spits this out every time:

Buildfile: /Users/324876/Documents/workspace/Tank Drive/build.xml
Trying to override old definition of task classloader
clean:
   [delete] Deleting directory /Users/324876/Documents/workspace/Tank Drive/build
compile:
    [mkdir] Created dir: /Users/324876/Documents/workspace/Tank Drive/build
     [echo] [athena-compile] Compiling src with classpath=/Users/324876/wpilib/java/current/lib/WPILib.jar:/Users/324876/wpilib/java/current/lib/NetworkTables.jar: to build
    [javac] Compiling 1 source file to /Users/324876/Documents/workspace/Tank Drive/build
    [javac] /Users/324876/Documents/workspace/Tank Drive/src/org/usfirst/frc/team4301/robot/Robot.java:4: cannot access edu.wpi.first.wpilibj.SampleRobot
    [javac] bad class file: edu/wpi/first/wpilibj/SampleRobot.class(edu/wpi/first/wpilibj:SampleRobot.class)
    [javac] class file has wrong version 52.0, should be 50.0
    [javac] Please remove or make sure it appears in the correct subdirectory of the classpath.
    [javac] import edu.wpi.first.wpilibj.SampleRobot;
    [javac]                             ^

BUILD FAILED
/Users/324876/wpilib/java/current/ant/build.xml:71: Compile failed; see the compiler error output for details.

Total time: 2 seconds

It is just one of the example programs, so I know that there is not a problem with my code. Has anybody seen this before? What should I do to fix it?