Fixed compilation on JDK 7
Fixed compilation on JDK 7

apangin/async-profiler,apangin/async-profiler,jvm-profiling-tools/async-profiler,jvm-profiling-tools/async-profiler,jvm-profiling-tools/async-profiler,jvm-profiling-tools/async-profiler,apangin/async-profiler,jvm-profiling-tools/async-profiler,apangin/async-profiler