Information-hiding in Groovy (using closures? naming conventions?)

SecurityManager

don't run following code from GroovyConsole. only from groovy command line.

def sm = new SecurityManager()
System.setSecurityManager(sm)
//without previous lines the following code will run successfully
println new ByteArrayOutputStream().buf

this will throw the following exception

Caught: java.security.AccessControlException: access denied ("java.lang.RuntimePermission" "accessDeclaredMembers")
java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.codehaus.groovy.tools.GroovyStarter.rootLoader(GroovyStarter.java:109)
        at org.codehaus.groovy.tools.GroovyStarter.main(GroovyStarter.java:131)
Caused by: java.lang.ExceptionInInitializerError
        at groovy.ui.GroovyMain.run(GroovyMain.java:397)
        at groovy.ui.GroovyMain.process(GroovyMain.java:370)
        at groovy.ui.GroovyMain.processArgs(GroovyMain.java:129)
        at groovy.ui.GroovyMain.main(GroovyMain.java:109)
        ... 6 more
Caused by: java.security.AccessControlException: access denied ("java.util.logging.LoggingPermission" "control")
        at java.security.AccessControlContext.checkPermission(AccessControlContext.java:472)
        at java.security.AccessController.checkPermission(AccessController.java:884)
        at java.lang.SecurityManager.checkPermission(SecurityManager.java:549)
        at java.util.logging.LogManager.checkPermission(LogManager.java:1586)
        at java.util.logging.Logger.checkPermission(Logger.java:422)
        at java.util.logging.Logger.setUseParentHandlers(Logger.java:1799)
        at org.codehaus.groovy.runtime.StackTraceUtils.<clinit>(StackTraceUtils.java:57)
        ... 10 more

control access with getProperty & setProperty

class A extends GroovyObjectSupport{
    private int i=555
    private int j=666
    def f(){
        println "i=$i j=$j"
    }
    Object getProperty(String name){
        if(name in ['i'])throw new Exception("Access to property `$name` is denied")
        return super.getProperty(name)
    }
}
def a=new A()
a.f()
println "a.j = ${a.j}"
println "a.i = ${a.i}"

this will allow access to member j but not to the member i outside of class.

output:

i=555 j=666
a.j = 666
Exception thrown

java.lang.Exception: Access to property `i` is denied
  ...