getPID method get current process id improve speed

[chenyi19851209]

getPID method get current process id waste time,because of call
ManagementFactory.getRuntimeMXBean() every time. call only once ok.

public static long getPID() {
String processName = java.lang.management.ManagementFactory.getRuntimeMXBean().getName();
if (processName != null && processName.length() > 0) {
try {
return Long.parseLong(processName.split("@")[0]);
} catch (Exception e) {
return 0;
}
}
return 0;
}