JavaSE---The Platform Environment

1、Configuration Utilities

　　　　This section describes some of the configuration utilities that help an application access its startup context.

　　　　1.1、Properties

　　　　　　　　Properties are configuration values managed as key/value pairs.

　　　　　　　　In each pair, the key and value are both String values.

　　　　　　　　To manage properties, create instances of java.util.Properties.

　　　　　　　　The System class maintains a Properties object that defines the configuration of the current working environment.

　　　　1.2、Command-Line Arguments

　　　　　　　　A Java application can accept any number of arguments from the command line.

　　　　　　　　This allows the user to specify configuration information when the application is launched.

　　　　1.3、Environment Variables

　　　　　　　　Many operating systems use environment variables to pass configuration information to applications.（许多操作系统 使用 环境变量  传递配置信息给应用）

　　　　　　　　Querying Environment Variables

　　　　　　　　　　On the Java platform, an application uses System.getenv to retrieve environment variable values.

　　　　　　　　　　Environment variables are key/value pairs, where both the key and the value are strings.