java.security

java.security

出于java的安全限制，System.getProperty("line.seperator")是不能够直接取得的。可以这样做：

String lineSeparator  =  (String) java.security.AccessController.doPrivileged(
                new  sun.security.action.GetPropertyAction( " line.separator " ));

具体参考java.io.BufferedWriter的源代码就可以找到上面这行代码。 DriverManager里也有

 1       private   static   void  loadInitialDrivers() {
 2          String drivers;
 3 
 4           try  {
 5              drivers  =  (String) java.security.AccessController
 6                      .doPrivileged( new  sun.security.action.GetPropertyAction(
 7                               " jdbc.drivers " ));
 8          }  catch  (Exception ex) {
 9              drivers  =   null ;
10          }
11          println( " DriverManager.initialize: jdbc.drivers =  "   +  drivers);
12           if  (drivers  ==   null ) {
13               return ;
14          }
15           while  (drivers.length()  !=   0 ) {
16               int  x  =  drivers.indexOf( ' : ' );
17              String driver;
18               if  (x  <   0 ) {
19                  driver  =  drivers;
20                  drivers  =   "" ;
21              }  else  {
22                  driver  =  drivers.substring( 0 , x);
23                  drivers  =  drivers.substring(x  +   1 );
24              }
25               if  (driver.length()  ==   0 ) {
26                   continue ;
27              }
28               try  {
29                  println( " DriverManager.Initialize: loading  "   +  driver);
30                  Class.forName(driver,  true , ClassLoader.getSystemClassLoader());
31              }  catch  (Exception ex) {
32                  println( " DriverManager.Initialize: load failed:  "   +  ex);
33              }
34          }
35      }

sun.security.action.GetPropertyAction() hasn't been publiced.actually and exactly,it's not be doced,which reflects that sun doesn't surport us to use these class or method which is lower class,usually, we use the classes api tells us is proier and maybe has called these undoc class  but usually for us ,it's not necessary.so in the program of us or even others ,we could and i think it's really better for us to neglect  them which u can find out in the jar file of rt.jar.