Java的System类实战

怼烎@ 2021-09-29 07:16 281阅读 0赞

**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<String, String> 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 Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules
    SystemDrive=C:
    USERNAME=cakin
    ProgramFiles(x86)=C:\Program Files (x86)
    FPS_BROWSER_USER_PROFILE_STRING=Default
    PYTHONPATH=.;E:\Python\MySQLControler
    PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
    DriverData=C:\Windows\System32\Drivers\DriverData
    ......

**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:\Program\Java\jdk1.8.0_162\bin;C:\WINDOWS\Sun\Java\bin;C:\WINDOWS\system32;C:\WINDOWS;C:\ProgramData\Oracle\Java\javapath;C:\Program Files (x86)\Intel\iCLS Client\;C:\Program Files\Intel\iCLS Client\;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files\Intel\Intel(R) Management Engine Components\DAL;C:\Program Files (x86)\Intel\Intel(R) Management Engine Components\IPT;C:\Program Files\Intel\Intel(R) Management Engine Components\IPT;D:\Program Files (x86)\scala\bin;D:\Program Files\nodejs\;C:\WINDOWS\System32\OpenSSH\;D:\Program Files\Git\cmd;C:\Users\cakin\AppData\Local\Microsoft\WindowsApps;D:\Program\hadoop-2.7.4\bin;D:\Program\Java\jdk1.8.0_162\bin;C:\Program Files\Microsoft VS Code\bin;D:\Program\apache-maven-3.5.3\bin;C:\Users\cakin\AppData\Roaming\npm;D:\Program\gradle-2.14\bin;D:\Programs\Fiddler;D:\Python27;D:\Python27\Scripts;D:\Anaconda3;D:\Anaconda3\Scripts;D:\Anaconda3\Library\bin;E:\Django\ComPerformance\venv\Lib\site-packages\django;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
    ......