String getproperty (string key, string DEF)

String getproperty (string key, string DEF) gets the system attribute described with the specified key. * If the key is the key of the configuration file such as the key system environment or properties, such as OS. name, return the value of the key * If the key is null or null, an error is returned! Key can't be empty key can't be null * If the key is not null, It is not null, or the key of the configuration file such as the system environment or properties, the def value is returned.

DEMO code:

Package COM. test; public class test {public static void main (string [] ARGs) {testsetgetproperty ();} public static void testsetgetproperty () {string str1, str2, str3; str1 = system. getproperty ("Java. version "); str2 = system. getproperty ("user. dir "); // str3 = system. getproperty (""); // The error key can't be empty system is returned. out. println (str2); system. out. println (str1);/* getproperty (string key, string DEF) gets the system genus described with the specified key * If the key of the configuration file such as the key system environment or properties, such as OS. Name, returns the value of the key * If the key is null or null, an error is returned! Key can't be empty key can't be null * If the key is not null, It is not null, or the key of the configuration file such as the system environment or properties, returns the def value **/string str4, str5, str6; str4 = system. getproperty ("OS. name "," mydefault "); // str5 = system. getproperty (null, "mydefault"); // The error key can't be null str6 = system. getproperty ("AAA", "mydefault"); // The output mydefault is not the system key of the configuration file such as the system environment or properties. out. println (str4); // output Windows 7 // system. out. println (str5); system. out. println (str6); // default output value: mydefault }}

 

　　　　　　　　　　Key-value pairs of configuration files such as system environment or properties

Java. Version	Java Runtime Environment version
Java. Vendor	Java Runtime Environment vendor
Java. Vendor. url	Java vendor URL
Java. Home	Java installation directory
Java. VM. Specification. Version	Java Virtual Machine standard version
Java. VM. Specification. Vendor	Java virtual machine specification vendor
Java. VM. Specification. Name	Java virtual machine specification name
Java. VM. Version	Java Virtual Machine implementation version
Java. VM. Vendor	Java Virtual Machine implementation vendor
Java. VM. Name	Java Virtual Machine implementation name
Java. Specification. Version	Java Runtime Environment Standard version
Java. Specification. Vendor	Java Runtime Environment specification vendor
Java. Specification. Name	Java Runtime Environment specification name
Java. Class. Version	Java format version number
Java. Class. Path	Java class path
Java. Library. Path	List of search paths when the library is loaded
Java. Io. tmpdir	Default temporary file path
Java. Compiler	Name of the JIT compiler to be used
Java. Ext. dirs	Path of one or more extended Directories
OS. Name	Operating system name
OS. Arch	Operating System Architecture
OS. Version	Operating system version
File. Separator	File separator ("/" in UNIX)
Path. Separator	Path separator (":" in UNIX)
Line. Separator	Line separator ("/n" in UNIX ")
User. Name	User Account Name
User. Home	User's home directory
User. dir	Current working directory of the user