java的-D选项作用

1.java已有默认系统属性，通过：System.getProperties().list(System.out);查看，结果如下：

-- listing properties --

java.runtime.name=Java(TM) SE Runtime Environment

sun.boot.library.path=D:\java\jdk1.6.0_23\jre\bin

java.vm.version=19.0-b09

java.vm.vendor=Sun Microsystems Inc.

java.vendor.url=http://java.sun.com/

path.separator=;

java.vm.name=Java HotSpot(TM) Client VM

file.encoding.pkg=sun.io

user.country=CN

sun.java.launcher=SUN_STANDARD

sun.os.patch.level=

java.vm.specification.name=Java Virtual Machine Specification

user.dir=E:\workspace\javad\javad

java.runtime.version=1.6.0_23-b05

java.awt.graphicsenv=sun.awt.Win32GraphicsEnvironment

java.endorsed.dirs=D:\java\jdk1.6.0_23\jre\lib\endorsed

os.arch=x86

java.io.tmpdir=C:\Users\ADMINI~1\AppData\Local\Temp\

line.separator=

java.vm.specification.vendor=Sun Microsystems Inc.

user.variant=

os.name=Windows 7

sun.jnu.encoding=GBK

java.library.path=D:\java\jdk1.6.0_23\bin;.;C:\Windows\...

java.specification.name=Java Platform. API Specification

java.class.version=50.0

sun.management.compiler=HotSpot Client Compiler

os.version=6.1

user.home=C:\Users\Administrator

user.timezone=

java.awt.printerjob=sun.awt.windows.WPrinterJob

file.encoding=GBK

java.specification.version=1.6

user.name=Administrator

java.class.path=E:\workspace\javad\javad\target\test-...

java.vm.specification.version=1.0

sun.arch.data.model=32

java.home=D:\java\jdk1.6.0_23\jre

java.specification.vendor=Sun Microsystems Inc.

user.language=zh

awt.toolkit=sun.awt.windows.WToolkit

java.vm.info=mixed mode, sharing

java.version=1.6.0_23

java.ext.dirs=D:\java\jdk1.6.0_23\jre\lib\ext;C:\Wi...

sun.boot.class.path=D:\java\jdk1.6.0_23\jre\lib\resources...

java.vendor=Sun Microsystems Inc.

file.separator=\

java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport...

sun.cpu.endian=little

sun.io.unicode.encoding=UnicodeLittle

sun.desktop=windows

sun.cpu.isalist=pentium_pro+mmx pentium_pro pentium+m...

2.可以使用java -D修改这些属性，也可以创建自己的程序属性，如：java -Djava.io.tmpdir=d:\，修改临时文件存放目录