-client to select the "client" VM
-hotspot is a synonym for the "hotspot" VM [deprecated]
-server to select the "server" VM
-classic to select the "classic" VM
If present, the option to select the VM must be first.
The default VM is -client.
用java -X命令可列出如下选项
-Xmixed mixed mode execution (default)
-Xint interpreted mode execution only
-Xbootclasspath:<directories and zip/jar files separated by ;>
set search path for bootstrap classes and resources
-Xbootclasspath/a:<directories and zip/jar files separated by ;>
append to end of bootstrap class path
-Xbootclasspath/p:<directories and zip/jar files separated by ;>
prepend in front of bootstrap class path
-Xnoclassgc disable class garbage collection
-Xincgc enable incremental garbage collection
-Xbatch disable background compilation
-Xms<size> set initial Java heap size
-Xmx<size> set maximum Java heap size
-Xss<size> set java thread stack size
-Xprof output cpu profiling data
-Xrunhprof[:help]|[:<option>=<value>, ...]
perform JVMPI heap, cpu, or monitor profiling
-Xdebug enable remote debugging
-Xfuture enable strictest checks, anticipating future default
-Xrs reduce use of OS signals by Java/VM
请高手解释一下这些参数的意思，哪几个最有用，应该在什么情况下使用，对程序性能有什么影响？
