Testing Service from RestController by calling it multiple times simultaneously(Load Testing i mean for multi user)

I want to test My RestApi for multi user concurrency.Is there any way other than Jmeter,Load Runner? I mean i want to test like Junit not with any tool.I have tried using Multithreading but its not working.I am new to multithreading concept too .I just want to call my service from restController mutliple times simultaneously and check response.