Inorder to accurately point the lines of code causing the CPU spike, you need to analyze not only thread dumps but also 'top -H -p {PID}' command output, where {PID} is your Java application's process Id which is experiencing CPU spike. When you issue this ‘top’ command with given arguments, it will list all the threads running in the application and amount of CPU each one of the thread consume. Once you have both the data, you can identify high CPU consuming thread and lines of code they are executing.
You can use the open source yCrash script which will capture 360-degree application level artifacts (like GC logs, 3 snapshots of thread dumps, heap dumps) and system level artifacts (like top, top -H, netstat, vmstat, iostat, dmesg, diskusage, kernel parameters...). Once you have these data, either you can manually analyze them or upload it to yCrash tool. Tool analyzes all these dataset and generates an instant root cause analysis report pointing out exact line of code causing the CPU spike. Here is more detailed information on how to diagnose high CPU spike.
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