系統屬性是指與用戶程式相關的作業系統配置信息以及軟體信息。通常與用戶程式相關的屬性關鍵字包括：
●file.separator:檔案分隔設定，Windows環境下為“"，Unix環境下為“/”；
●user.home：用戶主目錄；
●java.home：Java實時運行環境的安裝目錄；
●java.ext.dirs：JDK的安裝目錄；
●os.name：作業系統名稱；
●user.name：用戶登錄名稱；
●os.version：作業系統版本；
●path.separator：當前作業系統的路徑分隔設定；
●user.dir：當前用戶程式所在目錄。
如果想要查看所有的系統屬性，可以編寫如下代碼sysEnv.java
import java.util.Iterator;
import java.util.Properties;
public class sysEnv {
public static void main(String args[])
{
Properties props=System.getProperties();
Iterator iter=props.keySet().iterator();
while(iter.hasNext())
{
String key=(String)iter.next();
System.out.println(key+" = "+ props.get(key));
}
}
}
運行此java代碼，就可以看到所有的系統屬性和對應的值了。
例如，我本機運行後的結果：
java.runtime.name = Java(TM) 2 Runtime Environment, Standard Edition
sun.boot.library.path = C:\j2sdk1.4.2_09\jre\bin
java.vm.version = 1.4.2_09-b05
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.os.patch.level = Service Pack 2
java.vm.specification.name = Java Virtual Machine Specification
user.dir = E:\eclipse\testDemo
java.runtime.version = 1.4.2_09-b05
java.awt.graphicsenv = sun.awt.Win32GraphicsEnvironment
java.endorsed.dirs = C:\j2sdk1.4.2_09\jre\lib\endorsed
os.arch = x86
java.io.tmpdir = C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp\
line.separator =
java.vm.specification.vendor = Sun Microsystems Inc.
user.variant =
os.name = Windows XP
sun.java2d.fontpath =
java.library.path = C:\j2sdk1.4.2_09\bin;.;C:\WINDOWS\system32;C:\WINDOWS;C:\j2sdk1.4.2_09\bin;d:\oracle\ora92\bin;C:\Program Files\Oracle\jre\1.1.8\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\WBEM;D:\MySQL\MySQL Server 4.1\bin;d:\Program Files\IDM Computer Solutions\UltraEdit-32
java.specification.name = Java Platform API Specification
java.class.version = 48.0
java.util.prefs.PreferencesFactory = java.util.prefs.WindowsPreferencesFactory
os.version = 5.1
user.home = C:\Documents and Settings\Administrator
user.timezone =
java.awt.printerjob = sun.awt.windows.WPrinterJob
file.encoding = GBK
java.specification.version = 1.4
java.class.path = E:\eclipse\testDemo\bin;E:\eclipse\lucene-1.4.3\lucene-2.0.0\lucene-2.0.0\lucene-core-2.0.0.jar;E:\Library\commons\commons-io-1.1.jar;E:\Library\commons\commons-net-1.1.0.jar;F:\everyday\6月\15\je-analysis-1[1].2.2.jar;E:\Library\junit\junit.jar
user.name = Cral
java.vm.specification.version = 1.0
java.home = C:\j2sdk1.4.2_09\jre
sun.arch.data.model = 32
user.language = zh
java.specification.vendor = Sun Microsystems Inc.
awt.toolkit = sun.awt.windows.WToolkit
java.vm.info = mixed mode
java.version = 1.4.2_09
java.ext.dirs = C:\j2sdk1.4.2_09\jre\lib\ext
sun.boot.class.path = C:\j2sdk1.4.2_09\jre\lib\rt.jar;C:\j2sdk1.4.2_09\jre\lib\i18n.jar;C:\j2sdk1.4.2_09\jre\lib\sunrsasign.jar;C:\j2sdk1.4.2_09\jre\lib\jsse.jar;C:\j2sdk1.4.2_09\jre\lib\jce.jar;C:\j2sdk1.4.2_09\jre\lib\charsets.jar;C:\j2sdk1.4.2_09\jre\classes
java.vendor = Sun Microsystems Inc.
file.separator = \
java.vendor.url.bug = http://java.sun.com/cgi-bin/bugreport.cgi
sun.io.unicode.encoding = UnicodeLittle
sun.cpu.endian = little
sun.cpu.isalist = pentium i486 i386
