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java虚拟机参数说明

时间:2009-12-16 01:10来源:未知 作者:admin 点击:
下面的内容是从sun网站上找到的java虚拟机参数说明,包含标准的和非标准的,但不包含-XX的非标准不稳定选项。 对于-XX选项请参考站点上的其他文章。 标准选项 -client Select the Java HotSpot Client VM.
  

下面的内容是从sun网站上找到的java虚拟机参数说明,包含标准的和非标准的,但不包含-XX的非标准不稳定选项。

对于-XX选项请参考站点上的其他文章。

标准选项

    -client
        Select the Java HotSpot Client VM.

        For more information, see Server-Class Machine Detection

    -server
        Select the Java HotSpot Server VM.

        For more information, see Server-Class Machine Detection

    -agentlib:libname[=options]
        Load native agent library libname, e.g.

        -agentlib:hprof

        -agentlib:jdwp=help

        -agentlib:hprof=help

        For more information, see JVMTI Agent Command Line Options.

    -agentpath:pathname[=options]
        Load a native agent library by full pathname. For more information, see JVMTI Agent Command Line Options.
    -classpath classpath
    -cp classpath
        Specify a list of directories, JAR archives, and ZIP archives to search for class files. Class path entries are separated by colons (:). Specifying -classpath or -cp overrides any setting of the CLASSPATH environment variable.

        If -classpath and -cp are not used and CLASSPATH is not set, the user class path consists of the current directory (.).

        For more information on class paths, see Setting the Class Path.

    -Dproperty=value
        Set a system property value.

    -d32
    -d64
        Specifies whether the program is to be run in a 32-bit or 64-bitenvironment if available.

        Currently only the Java HotSpot Server VM supports 64-bit operation, and the "-server" option is implicit with the use of -d64. This is subject to change in a future release.

        If neither -d32 nor -d64 is specified, the default is to run in a 32-bit environment, except for 64-bit onlysystems. This is subject to change in a future release.

    -enableassertions[:<package name>"..." | :<class name> ]
    -ea[:<package name>"..." | :<class name> ]
        Enable assertions. Assertions are disabled by default.

        With no arguments, enableassertions or -ea enables assertions. With oneargument ending in "...", the switch enables assertions in thespecified package and any subpackages. If the argument is simply"...", the switch enables assertions in the unnamed package in the currentworking directory. With one argument not ending in "...", the switchenables assertions in the specified class.

        If a single command line contains multiple instances of these switches, they are processed in order before loading any classes. So, for example, to run a program with assertions enabled only in package com.wombat.fruitbat (and any subpackages), the followingcommand could be used:

        java -ea:com.wombat.fruitbat... <Main Class>

        The -enableassertions and -ea switches apply to all class loaders and to system classes(which do not have a class loader). There is one exception to this rule:in their no-argument form, the switches do not apply to system.This makes it easy to turn on asserts in all classes except for systemclasses. A separate switch is provided to enable asserts in all systemclasses; see -enablesystemassertions below.

    -disableassertions[:<package name>"..." | :<class name> ]
    -da[:<package name>"..." | :<class name> ]
        Disable assertions. This is the default.

        With no arguments, disableassertions or -da disables assertions. With oneargument ending in "...", the switch disables assertions in thespecified package and any subpackages. If the argument is simply"...", the switch disables assertions in the unnamed package in the currentworking directory. With one argument not ending in "...", the switchdisables assertions in the specified class.

        To run a program with assertions enabled in packagecom.wombat.fruitbat but disabled in classcom.wombat.fruitbat.Brickbat, the following command couldbe used:

        java -ea:com.wombat.fruitbat... -da:com.wombat.fruitbat.Brickbat <Main Class>

        The -disableassertions and -da switches apply to all class loaders and to system classes(which do not have a class loader). There is one exception to this rule:in their no-argument form, the switches do not apply to system.This makes it easy to turn on asserts in all classes except for systemclasses. A separate switch is provided to enable asserts in all systemclasses; see -disablesystemassertions below.

    -enablesystemassertions
    -esa
        Enable asserts in all system classes (sets the default assertion status for system classes to true).

    -disablesystemassertions
    -dsa
        Disables asserts in all system classes.

    -jar
        Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial for information about working with Jar files and Jar-file manifests.

        When you use this option, the JAR file is the source of all user classes, and other user class path settings are ignored.

        Note that JAR files that can be run with the "java -jar" option can have their execute permissions set so they can be run without using "java -jar". Refer to Java Archive (JAR) Files.

    -javaagent:jarpath[=options]
        Load a Java programming language agent, seejava.lang.instrument.


    -verbose
    -verbose:class
        Display information about each class loaded.


    -verbose:gc
        Report on each garbage collection event.

    -verbose:jni
        Report information about use of native methods and other Java Native Interface activity.

    -version
        Display version information and exit.

    -showversion
        Display version information and continue.

    -?
    -help
        Display usage information and exit.

    -X
        Display information about non-standard options and exit.


非标准选项


-Xint
    Operate in interpreted-only mode. Compilation to native code is disabled, and all bytecodes are executed by the interpreter. The performance benefits offered by the Java HotSpot VMs' adaptive compiler will not be present in this mode.

-Xbatch
    Disable background compilation. Normally the VM will compile the method as a background task, running the method in interpreter mode until the background compilation is finished. The -Xbatch flag disables background compilation so that compilation of all methods proceeds as a foreground task until completed.

-Xdebug
    Start with support for JVMDI enabled. JVMDI has been deprecated and is not used for debugging in J2SE 5.0, so this option isn't needed for debugging in J2SE 5.0.

-Xbootclasspath:bootclasspath
    Specify a colon-separated list of directories, JAR archives, and ZIP archives to search for boot class files. These are used in place of the boot class files included in the Java 2 SDK. Note: Applications that use this option for the purpose of overriding a class in rt.jar should not be deployed as doing so would contravene the Java 2 Runtime Environment binary code license.

-Xbootclasspath/a:path
    Specify a colon-separated path of directires, JAR archives, and ZIP archives to append to the default bootstrap class path.
-Xbootclasspath/p:path
    Specify a colon-separated path of directires, JAR archives, and ZIP archives to prepend in front of the default bootstrap class path. Note: Applications that use this option for the purpose of overriding a class in rt.jar should not be deployed as doing so would contravene the Java 2 Runtime Environment binary code license.

-Xcheck:jni
    Perform additional checks for Java Native Interface (JNI) functions. Specifically, the Java Virtual Machine validates the parameters passed to the JNI function as well as the runtime environment data before processing the JNI request. Any invalid data encountered indicates a problem in the native code, and the Java Virtual Machine will terminate with a fatal error in such cases. Expect a performance degradation when this option is used.

-Xfuture
    Perform strict class-file format checks. For purposes of backwards compatibility, the default format checks performed by the Java 2 SDK's virtual machine are no stricter than the checks performed by 1.1.x versions of the JDK software. The -Xfuture flag turns on stricter class-file format checks that enforce closer conformance to the class-file format specification. Developers are encouraged to use this flag when developing new code because the stricter checks will become the default in future releases of the Java application launcher.

-Xnoclassgc
    Disable class garbage collection.

-Xincgc
    Enable the incremental garbage collector. The incremental garbage collector, which is off by default, will reduce the occasional long garbage-collection pauses during program execution. The incremental garbage collector will at times execute concurrently with the program and during such times will reduce the processor capacity available to the program.

-Xloggc:file
    Report on each garbage collection event, as with -verbose:gc, but log this data to file. In addition to the information -verbose:gc gives, each reported event will be preceeded by the time (in seconds) since the first garbage-collection event.

    Always use a local file system for storage of this file to avoid stalling the JVM due to network latency. The file may be truncated in the case of a full file system and logging will continue on the truncated file. This option overrides -verbose:gc if both are given on the command line.

-Xmsn
    Specify the initial size, in bytes, of the memory allocation pool. This value must be a multiple of 1024 greater than 1MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is 2MB. Examples:

               -Xms6291456
               -Xms6144k
               -Xms6m
             

-Xmxn
    Specify the maximum size, in bytes, of the memory allocation pool. This value must a multiple of 1024 greater than 2MB. Append the letter k or K to indicate kilobytes, or m or M to indicate megabytes. The default value is 64MB. Examples:

               -Xmx83886080
               -Xmx81920k
               -Xmx80m
             

    On Solaris 7 and Solaris 8 SPARC platforms,the upper limit for this value is approximately 4000mminus overhead amounts. On Solaris 2.6 and x86 platforms, the upper limit is approximately 2000m minus overhead amounts. On Linux platforms, the upper limit is approximately 2000m minus overhead amounts.

-Xprof
    Profiles the running program, and sends profiling data to standard output. This option is provided as a utility that is useful in program development and is not intended to be be used in production systems.

-Xrunhprof[:help][:<suboption>=<value>,...]
    Enables cpu, heap, or monitor profiling. This option is typically followed by a list of comma-separated "<suboption>=<value>" pairs.Run the command java -Xrunhprof:help to obtain a list of suboptions and their default values.

-Xrs
    Reduces use of operating-system signals by the Java virtual machine (JVM).

    In a previous release, the Shutdown Hooks facility was added to allow orderly shutdown of a Java application. The intent was to allow user cleanup code (such as closing database connections) to run at shutdown, even if the JVM terminates abruptly.

    Sun's JVM catches signals to implement shutdown hooks for abnormal JVM termination. The JVM uses SIGHUP, SIGINT, and SIGTERM to initiate the running of shutdown hooks.

    The JVM uses a similar mechanism to implement the pre-1.2 feature of dumping thread stacks for debugging purposes. Sun's JVM uses SIGQUIT to perform thread dumps.

    Applications embedding the JVM frequently need to trap signals like SIGINT or SIGTERM, which can lead to interference with the JVM's own signal handlers. The -Xrs command-line option is available to address this issue. When -Xrs is used on Sun's JVM, the signal masks for SIGINT, SIGTERM, SIGHUP, and SIGQUIT are not changed by the JVM, and signal handlers for these signals are not installed.

    There are two consequences of specifying -Xrs:

        * SIGQUIT thread dumps are not available.
        * User code is responsible for causing shutdown hooks to run, for example by calling System.exit() when the JVM is to be terminated.


-Xssn
    Set thread stack size.

 

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