java中System.getProperties()与System.getEnv()

其实在运行虚拟机时，经常一些虚拟机参数或者系统参数

getEnv()方法

System.getEnv()可以获取到我们在操作系统中的设置的一些环境变量

public static void testGetEnv() {
        Map<String, String> env = System.getenv();
        for(String key:env.keySet()) {
            System.out.println(key+"="+env.get(key));
        }
    }

结果运行

USERDOMAIN_ROAMINGPROFILE=LAPTOP-L8MRCMCM
LOCALAPPDATA=C:Usershua'weiAppDataLocal
PROCESSOR_LEVEL=6
USERDOMAIN=LAPTOP-L8MRCMCM
FPS_BROWSER_APP_PROFILE_STRING=Internet Explorer
LOGONSERVER=\LAPTOP-L8MRCMCM
JAVA_HOME=D:programjdk-15
SESSIONNAME=Console
ALLUSERSPROFILE=C:ProgramData
PROCESSOR_ARCHITECTURE=AMD64
PSModulePath=C:Program FilesWindowsPowerShellModules;C:Windowssystem32WindowsPowerShellv1.0Modules
SystemDrive=C:
MAVEN_HOME=D:programapache-maven-3.6.3
OneDrive=C:Usershua'weiOneDrive
APPDATA=C:Usershua'weiAppDataRoaming
USERNAME=hua'wei
ProgramFiles(x86)=C:Program Files (x86)
CommonProgramFiles=C:Program FilesCommon Files
Path=D:/program/sts-4.8.0.RELEASE//plugins/org.eclipse.justj.openjdk.hotspot.jre.full.win32.x86_64_14.0.2.v20200815-0932/jre/bin/server;D:/program/sts-4.8.0.RELEASE//plugins/org.eclipse.justj.openjdk.hotspot.jre.full.win32.x86_64_14.0.2.v20200815-0932/jre/bin;D:programvmware_workstationin;C:Windowssystem32;C:Windows;C:WindowsSystem32Wbem;C:WindowsSystem32WindowsPowerShellv1.0;C:WindowsSystem32OpenSSH;C:Program Files (x86)NVIDIA CorporationPhysXCommon;C:Program FilesNVIDIA CorporationNVIDIA NvDLISR;D:programjdk-15in;D:programjdk-15jrein;D:programapache-maven-3.6.3in;D:programmysql-8.0.21-winx64in;C:Usershua'weiAppDataLocalMicrosoftWindowsApps;C:Program FilesBandizip;D:programsts-4.8.0.RELEASE;
FPS_BROWSER_USER_PROFILE_STRING=Default
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
DriverData=C:WindowsSystem32DriversDriverData
OS=Windows_NT
classpath=.;D:programjdk-15lib;D:programjdk-15lib	ools.jar 
COMPUTERNAME=LAPTOP-L8MRCMCM

上述的输出结果有的是系统自带的环境变量，有的是我们自己设置的系统变量.

getProperties()方法

getProperties()方法可以获取到java虚拟机方面的参数

    public static void testGetProperties() {
        Properties properties = System.getProperties();
        for(Object key:properties.keySet()) {
            Object object = properties.get(key);
            System.out.println(key+"="+object);
        }
    }

输出结果

java.specification.version=15
sun.cpu.isalist=amd64
sun.jnu.encoding=GBK
java.class.path=D:workspacealgorithm-pro	argetclasses
java.vm.vendor=Oracle Corporation
sun.arch.data.model=64
user.variant=
java.vendor.url=https://java.oracle.com/
java.vm.specification.version=15
os.name=Windows 10
sun.java.launcher=SUN_STANDARD
user.country=CN
sun.boot.library.path=D:programjdk-15in
sun.java.command=com.resource.location.SystemDemo
jdk.debug=release
sun.cpu.endian=little
user.home=C:Usershua'wei
user.language=zh
java.specification.vendor=Oracle Corporation
java.version.date=2020-09-15
java.home=D:programjdk-15
file.separator=
java.vm.compressedOopsMode=Zero based
line.separator=

java.vm.specification.vendor=Oracle Corporation
java.specification.name=Java Platform API Specification
user.script=
sun.management.compiler=HotSpot 64-Bit Tiered Compilers
java.runtime.version=15+36-1562
user.name=hua'wei
path.separator=;
os.version=10.0
java.runtime.name=Java(TM) SE Runtime Environment
file.encoding=UTF-8
java.vm.name=Java HotSpot(TM) 64-Bit Server VM
java.vendor.url.bug=https://bugreport.java.com/bugreport/
java.io.tmpdir=C:Usershua'weiAppDataLocalTemp
java.version=15
user.dir=D:workspacealgorithm-pro
os.arch=amd64
java.vm.specification.name=Java Virtual Machine Specification
sun.os.patch.level=
java.library.path=D:programjdk-15in;C:WindowsSunJavain;C:Windowssystem32;C:Windows;D:/program/sts-4.8.0.RELEASE//plugins/org.eclipse.justj.openjdk.hotspot.jre.full.win32.x86_64_14.0.2.v20200815-0932/jre/bin/server;D:/program/sts-4.8.0.RELEASE//plugins/org.eclipse.justj.openjdk.hotspot.jre.full.win32.x86_64_14.0.2.v20200815-0932/jre/bin;D:programvmware_workstationin;C:Windowssystem32;C:Windows;C:WindowsSystem32Wbem;C:WindowsSystem32WindowsPowerShellv1.0;C:WindowsSystem32OpenSSH;C:Program Files (x86)NVIDIA CorporationPhysXCommon;C:Program FilesNVIDIA CorporationNVIDIA NvDLISR;D:programjdk-15in;D:programjdk-15jrein;D:programapache-maven-3.6.3in;D:programmysql-8.0.21-winx64in;C:Usershua'weiAppDataLocalMicrosoftWindowsApps;C:Program FilesBandizip;D:programsts-4.8.0.RELEASE;;.
java.vm.info=mixed mode, sharing
java.vendor=Oracle Corporation
java.vm.version=15+36-1562
sun.io.unicode.encoding=UnicodeLittle
java.class.version=59.0