Often time I come across situations where server comes under high CPU load. There is a simple way to find out which application thread(s) are responsible for the load. To get the thread which has the highest CPU load, issue:
ps -mo pid,lwp,stime,time,cpu -p
LWP stands for Light-Weight Process and typically refers to kernel threads. To identify the thread, get the LWP with highest CPU load, and convert its unique number (xxxx) into a hexadecimal number (0xxxx).
Get the java stack dump using jstack -l