Triggers the program execution. The environment will execute all parts of the program that have resulted in a "sink" operation. Sink operations are for example printing results ( {@link DataSet#print()}, writing results (e.g. {@link DataSet#writeAsText(String)}, {@link DataSet#write(eu.stratosphere.api.common.io.FileOutputFormat,String)}, or other generic data sinks created with {@link DataSet#output(eu.stratosphere.api.common.io.OutputFormat)}.
The program execution will be logged and displayed with a generated default name.
@return The result of the job execution, containing elapsed time and accumulators.
@throws Exception Thrown, if the program executions fails.