Why that my main class can't run?

[sunnypwang]

Error message from eclipse

my main class (I was trying to check isBiggerThan() method.)

[pakaponk]

First you created an Issue on the wrong repository na krub. This is 2110215_Exercise0_HelloGitHub, not 2110215_Lab1_Slave.
Please be careful next time because you might not be able to get an answer from TA.

About your question, please capture your "Package Explorer" also a "Configure Build Path ..." window so I can tell you what is going wrong?

If you don't know how to open "Configure Build Path ..." window, right click at your project -> Build Path -> Configure Build Path ...