Performance Testing for a back-end service in Java

If you are saying to create 100K+ calls per second by your program ,then use ThreadExecutor to create maximum threads you want to test for public methods in yours call. For example following code simaultaneously call yours public methods with 1000 threads accessing the methods

ExecutorService executor = Executors.newFixedThreadPool(1000);
         List<YourClass> callingList = new ArrayList<YourClass>();
         for (int i = 0; i < 1000; i++) {
             EntryPoint Impl = new EntryPoint (YourClass);
             callingList.add(Impl);
         }

 private Class EntryPoint implements Callable<Object>{
          private YourClass example;
     EntryPoint (YourClass  class) {
                this.example =  class;

            }
public List onCall() throws InterruptedException {
example.yourPublicMethod(); 

If you want to measure time taken by each threads for each methods use aspectJ for interceptor.You can record the time taken for each methods in a list through out the call of 1000 threads.Finally u can aagain iterate a list to get time taken for each on each methods .If you are looking for tools u can use VisualVM Or Jconsole.You can get information about CPU usuage,memory usuage ,threads status ,garbage collector,number of objects created and byte consumbed by objects and number of class loaded and many more .

JMeter works well for load testing.

http://jmeter.apache.org/