java命令也是SCJP必考內容,很有用處,即使你現在用的是IDE.
一、查看用法
| C:>java -help Usage: java [-options] class [args...] (to execute a class) or java [-options] -jar jarfile [args...] (to execute a jar file) where options include: -client to select the "client" VM -server to select the "server" VM -hotspot is a synonym for the "client" VM [deprecated] The default VM is client. -cp <class search path of directories and zip/jar files> -classpath <class search path of directories and zip/jar files> A ; separated list of directories, JAR archives, and ZIP archives to search for class files. -D<name>=<value> set a system property -verbose[:class|gc|jni] enable verbose output -version print product version and exit -version:<value> require the specified version to run -showversion print product version and continue -jre-restrict-search | -jre-no-restrict-search include/exclude user private JREs in the version search -? -help print this help message -X print help on non-standard options -ea[:<packagename>...|:<classname>] -enableassertions[:<packagename>...|:<classname>] enable assertions -da[:<packagename>...|:<classname>] -disableassertions[:<packagename>...|:<classname>] disable assertions -esa | -enablesystemassertions enable system assertions -dsa | -disablesystemassertions disable system assertions -agentlib:<libname>[=<options>] load native agent library <libname>, e.g. -agentlib:hprof see also, -agentlib:jdwp=help and -agentlib:hprof=help -agentpath:<pathname>[=<options>] load native agent library by full pathname -javaagent:<jarpath>[=<options>] load Java programming language agent, see java.lang.instrument |
這個命令幫助是英文的,不知道JDK咋搞的,也不妨礙使用.
另外,這個命令的非標準選項也是很重要的,常常在JVM優化配置方面很關鍵,可以參看本人的JVM參數配置文章.
| C:myproject>java -X -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 -Xloggc:<file> log GC status to a file with time stamps -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 -Xfuture enable strictest checks, anticipating future default -Xrs reduce use of OS signals by Java/VM (see documentation) -Xcheck:jni perform additional checks for JNI functions -Xshare:off do not attempt to use shared class data -Xshare:auto use shared class data if possible (default) -Xshare:on require using shared class data, otherwise fail. |
二、實踐
老規矩,主要看看裡面的參數（也叫開關）的使用.環境接著上篇javac的環境.
1、無參數情況
[火星人 ] JDK工具 java命令詳解已經有551次圍觀
