java.lang.management.ManagementFactory
java.lang.management.RuntimeMXBean



String name = ManagementFactory.getRuntimeMXBean().getName();  
// 5962@dugang.local
System.out.println(name);  
// 
String pid = name.split("@")[0];  
System.out.println("JVM pid is:" + pid); 


jdk9
System.out.println(ProcessHandle.current().pid());

jdk10
final RuntimeMXBean runtime = ManagementFactory.getRuntimeMXBean();
final long pid = runtime.getPid();