Java用System读取系统相关信息、环境变量——（六）

package Java_Test;

public class System1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
System.out.println(System.getProperty("java.version"));
System.out.println(System.getProperty("java.vendor"));
System.out.println(System.getProperty("java.home"));
System.out.println(System.getProperty("java.library.path"));
System.out.println(System.getProperty("user.dir"));   //获取当前类工作目录
System.out.println(System.getProperty("os.version"));
System.out.println(System.getProperty("os.name"));
System.out.println(System.getenv("path"));
    }

}

补充:获取系统所有属性的方法

package com.test;

import java.util.Properties;

public class MyTest {
    public static void main(String[] args) {
        Properties properties = System.getProperties();
        for (Object key : properties.keySet()) {
            System.out.println(key + " : " + properties.getProperty((String) key));
        }
    }
}

源码查看:所有的属性都存在System的一个内部属性Properties中，Properties是一个继承HashTable的类

(1)System.getProperties

    public static Properties getProperties() {
        SecurityManager sm = getSecurityManager();
        if (sm != null) {
            sm.checkPropertiesAccess();
        }

        return props;
    }

private static Properties props;

(2)Properties是一个继承HashTable的类

public
class Properties extends Hashtable<Object,Object> {

     private static final long serialVersionUID = 4112578634029874840L;

    protected Properties defaults;
。。。
}

结果:

java.runtime.name : Java(TM) SE Runtime Environment
sun.boot.library.path : C:Program FilesJavajdk1.7.0_80jrein
java.vm.version : 24.80-b11
java.vm.vendor : Oracle Corporation
java.vendor.url : http://java.oracle.com/
path.separator : ;
java.vm.name : Java HotSpot(TM) 64-Bit Server VM
file.encoding.pkg : sun.io
user.country : CN
user.script : 
sun.java.launcher : SUN_STANDARD
sun.os.patch.level : 
java.vm.specification.name : Java Virtual Machine Specification
user.dir : E:xiangmuMytest
java.runtime.version : 1.7.0_80-b15
java.awt.graphicsenv : sun.awt.Win32GraphicsEnvironment
java.endorsed.dirs : C:Program FilesJavajdk1.7.0_80jrelibendorsed
os.arch : amd64
java.io.tmpdir : C:UsersADMINI~1AppDataLocalTemp
line.separator : 

java.vm.specification.vendor : Oracle Corporation
user.variant : 
os.name : Windows 8.1
sun.jnu.encoding : GBK
java.library.path : C:Program FilesJavajdk1.7.0_80in;C:WINDOWSSunJavain;C:WINDOWSsystem32;C:WINDOWS;C:/Program Files/Java/jdk1.7.0_80/bin/../jre/bin/server;C:/Program Files/Java/jdk1.7.0_80/bin/../jre/bin;C:/Program Files/Java/jdk1.7.0_80/bin/../jre/lib/amd64;C:oraclexeapporacleproduct11.2.0serverin;C:WINDOWSsystem32;C:WINDOWS;C:WINDOWSSystem32Wbem;C:WINDOWSSystem32WindowsPowerShellv1.0;E:softapache-maven-3.5.3in;C:WINDOWSSystem32OpenSSH;E:gitGitcmd;E:SVNin;C:UsersAdministratorAppDataLocalMicrosoftWindowsApps;E:softmavenapache-maven-3.3.9in;C:Program FilesMySQLMySQL Server 5.7in;C:Program FilesJavajdk1.7.0_80in;E:gitGitin;E:gitGitusrin;E:gitGit;C:Program FilesJavajdk1.7.0_80jrein;D:zdcontomcatzdc8loprogram;;E:softeclipseeclipse-jee-mars-1-win32-x86_64eclipse;;.
java.specification.name : Java Platform API Specification
java.class.version : 51.0
sun.management.compiler : HotSpot 64-Bit Tiered Compilers
os.version : 6.3
user.home : C:UsersAdministrator
user.timezone : 
java.awt.printerjob : sun.awt.windows.WPrinterJob
file.encoding : UTF-8
java.specification.version : 1.7
java.class.path : E:xiangmuMytestin;E:xiangmuMytestWebContentWEB-INFliblog4j-1.2.16.jar;E:xiangmuMytestWebContentWEB-INFlibslf4j-api-1.5.10.jar;E:xiangmuMytestWebContentWEB-INFlibslf4j-log4j12-1.5.10.jar;E:	omcatapache-tomcat-7.0.88libannotations-api.jar;E:	omcatapache-tomcat-7.0.88libcatalina-ant.jar;E:	omcatapache-tomcat-7.0.88libcatalina-ha.jar;E:	omcatapache-tomcat-7.0.88libcatalina-tribes.jar;E:	omcatapache-tomcat-7.0.88libcatalina.jar;E:	omcatapache-tomcat-7.0.88libecj-4.4.2.jar;E:	omcatapache-tomcat-7.0.88libel-api.jar;E:	omcatapache-tomcat-7.0.88libjasper-el.jar;E:	omcatapache-tomcat-7.0.88libjasper.jar;E:	omcatapache-tomcat-7.0.88libjsp-api.jar;E:	omcatapache-tomcat-7.0.88libservlet-api.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-api.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-coyote.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-dbcp.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-i18n-es.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-i18n-fr.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-i18n-ja.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-jdbc.jar;E:	omcatapache-tomcat-7.0.88lib	omcat-util.jar;E:	omcatapache-tomcat-7.0.88lib	omcat7-websocket.jar;E:	omcatapache-tomcat-7.0.88libwebsocket-api.jar
user.name : Administrator
java.vm.specification.version : 1.7
sun.java.command : com.test.MyTest
java.home : C:Program FilesJavajdk1.7.0_80jre
sun.arch.data.model : 64
user.language : zh
java.specification.vendor : Oracle Corporation
awt.toolkit : sun.awt.windows.WToolkit
java.vm.info : mixed mode
java.version : 1.7.0_80
java.ext.dirs : C:Program FilesJavajdk1.7.0_80jrelibext;C:WINDOWSSunJavalibext
sun.boot.class.path : C:Program FilesJavajdk1.7.0_80jrelib
esources.jar;C:Program FilesJavajdk1.7.0_80jrelib
t.jar;C:Program FilesJavajdk1.7.0_80jrelibsunrsasign.jar;C:Program FilesJavajdk1.7.0_80jrelibjsse.jar;C:Program FilesJavajdk1.7.0_80jrelibjce.jar;C:Program FilesJavajdk1.7.0_80jrelibcharsets.jar;C:Program FilesJavajdk1.7.0_80jrelibjfr.jar;C:Program FilesJavajdk1.7.0_80jreclasses
java.vendor : Oracle Corporation
file.separator : 
java.vendor.url.bug : http://bugreport.sun.com/bugreport/
sun.io.unicode.encoding : UnicodeLittle
sun.cpu.endian : little
sun.desktop : windows
sun.cpu.isalist : amd64

 补充:可以采用System.setProperties设置系统属性

    public static void main(String[] args) {
        System.setProperty("mykey", "myvalue");
        String property = System.getProperty("mykey");
        System.out.println(property);
        try {
            Thread.sleep(100 * 1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

我们可以在cmd窗口通过jinfo查看变量

C:UsersAdministrator>jps
1236
8544 MyTest
9384 Jps

C:UsersAdministrator>jinfo 8544
Attaching to process ID 8544, please wait...
Debugger attached successfully.
Server compiler detected.
JVM version is 24.80-b11
Java System Properties:

java.runtime.name = Java(TM) SE Runtime Environment
java.vm.version = 24.80-b11
sun.boot.library.path = C:Program FilesJavajdk1.7.0_80jrein
java.vendor.url = http://java.oracle.com/
java.vm.vendor = Oracle Corporation
path.separator = ;
file.encoding.pkg = sun.io
java.vm.name = Java HotSpot(TM) 64-Bit Server VM
sun.os.patch.level =
sun.java.launcher = SUN_STANDARD
user.script =
user.country = CN
user.dir = E:xiangmuMytest
java.vm.specification.name = Java Virtual Machine Specification
java.runtime.version = 1.7.0_80-b15
mykey = myvalue

补充:System可以获取系统的环境变量

        // 读取单个环境变量
        String str = System.getenv("JAVA_HOME");
        System.out.println(str);

        // 读取所有的环境变量
        Map<String, String> getenv = System.getenv();
        for (Map.Entry<String, String> entry : getenv.entrySet()) {
            System.out.println(entry.getKey() + "========" + entry.getValue());
        }

结果:

C:Program FilesJavajdk1.7.0_80
USERPROFILE========C:UsersAdministrator
ProgramData========C:ProgramData
PATHEXT========.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
Classpath========.;%JAVA_HOME%lib;%JAVA_HOME%lib	ools.jar
JAVA_HOME========C:Program FilesJavajdk1.7.0_80
MAVEN_HOME========E:softmavenapache-maven-3.3.9
.......

java的System.getProperty()方法可以获取的值:

java.version	Java 运行时环境版本
java.vendor	Java 运行时环境供应商
java.vendor.url	Java 供应商的 URL
java.home	Java 安装目录
java.vm.specification.version	Java 虚拟机规范版本
java.vm.specification.vendor	Java 虚拟机规范供应商
java.vm.specification.name	Java 虚拟机规范名称
java.vm.version	Java 虚拟机实现版本
java.vm.vendor	Java 虚拟机实现供应商
java.vm.name	Java 虚拟机实现名称
java.specification.version	Java 运行时环境规范版本
java.specification.vendor	Java 运行时环境规范供应商
java.specification.name	Java 运行时环境规范名称
java.class.version	Java 类格式版本号
java.class.path	Java 类路径
java.library.path	加载库时搜索的路径列表
java.io.tmpdir	默认的临时文件路径
java.compiler	要使用的 JIT 编译器的名称
java.ext.dirs	一个或多个扩展目录的路径
os.name	操作系统的名称
os.arch	操作系统的架构
os.version	操作系统的版本
file.separator	文件分隔符（在 UNIX 系统中是“/”）
path.separator	路径分隔符（在 UNIX 系统中是“:”）
line.separator	行分隔符（在 UNIX 系统中是“/n”）
user.name	用户的账户名称
user.home	用户的主目录
user.dir	用户的当前工作目录