Java System类用法实战案例

本文实例讲述了Java System类用法。分享给大家供大家参考，具体如下：

一 使用System类访问系统属性

1 代码

import java.util.Map;
public class SystemClassDemo
{
  public static void main(String[] args)
  {
    Map env = System.getenv();  // 获得系统的环境变量
    for (String name : env.keySet())
    {
      System.out.println(name + "=" + env.get(name));
    }
  }
}

2 运行

......
ALLUSERSPROFILE=C:ProgramData
PROCESSOR_ARCHITECTURE=AMD64
PSModulePath=C:Program FilesWindowsPowerShellModules;C:WINDOWSsystem32WindowsPowerShellv1.0Modules
SystemDrive=C:
USERNAME=cakin
ProgramFiles(x86)=C:Program Files (x86)
FPS_BROWSER_USER_PROFILE_STRING=Default
PYTHonPATH=.;E:PythonMySQLControler
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
DriverData=C:WindowsSystem32DriversDriverData
......

二 打印当前虚拟机的所有环境变量和值

1 代码

import java.util.Enumeration;
import java.util.Properties;
public class SystemInfo
{
  public static void main(String[] args)
  {
    Properties sp = System.getProperties(); //获得当前虚拟机的环境属性
    Enumeration e = sp.propertyNames(); //获得环境属性中所有的变量
    //循环打印出当前虚拟机的所有环境属性的变量和值
    while (e.hasMoreElements())
    {
      String key = (String) e.nextElement();
      System.out.println(key + " = " + sp.getProperty(key));
    }
  }
}

2 运行

......
user.variant =
os.name = Windows 10
sun.jnu.encoding = GBK
java.library.path = D:ProgramJavajdk1.8.0_162bin;C:WINDOWSSunJavabin;C:WINDOWSsystem32;C:WINDOWS;C:ProgramDataOracleJavajavapath;C:Program Files (x86)InteliCLS Client;C:Program FilesInteliCLS Client;C:WINDOWSsystem32;C:WINDOWS;C:WINDOWSSystem32Wbem;C:WINDOWSSystem32WindowsPowerShellv1.0;C:Program Files (x86)IntelIntel(R) Management Engine ComponentsDAL;C:Program FilesIntelIntel(R) Management Engine ComponentsDAL;C:Program Files (x86)IntelIntel(R) Management Engine ComponentsIPT;C:Program FilesIntelIntel(R) Management Engine ComponentsIPT;D:Program Files (x86)scalabin;D:Program Filesnodejs;C:WINDOWSSystem32OpenSSH;D:Program FilesGitcmd;C:UserscakinAppDataLocalMicrosoftWindowsApps;D:Programhadoop-2.7.4bin;D:ProgramJavajdk1.8.0_162bin;C:Program FilesMicrosoft VS Codebin;D:Programapache-maven-3.5.3bin;C:UserscakinAppDataRoamingnpm;D:Programgradle-2.14bin;D:ProgramsFiddler;D:Python27;D:Python27scripts;D:Anaconda3;D:Anaconda3scripts;D:Anaconda3Librarybin;E:DjangoComPerformancevenvLibsite-packagesdjango;d:Program Files (x86)Nmap;.
java.specification.name = Java Platform API Specification
java.class.version = 52.0
sun.management.compiler = HotSpot 64-Bit Tiered Compilers
os.version = 10.0
......

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