This means that 8.77 seconds was spent in "user mode", which means the time was spent executing the code that you wrote (your Java code). 0.50 seconds was spent in "system mode", executing code for the operating system that was necessary during your code's execution. The total elapsed time for your program's execution was 12.38 seconds. Thus, your program occupied 74.8% of the computer's attention. The remaining time was spent for some other program, or some OS process, or simply idle.