question: public Node ( String permission , boolean value , boolean override , long expireAt , String server , String world , ContextSet contexts ) { if ( permission == null || permission . equals ( "" ) ) { throw new IllegalArgumentException ( "Empty permission" ) ; } if ( server != null && ( server . equalsIgnoreCase ( "global" ) || server . equals ( "" ) ) ) { server = null ; } if ( world != null && world . equals ( "" ) ) { world = null ; } if ( world != null && server == null ) { server = "global" ; } this . permission = permission ; this . value = value ; this . override = override ; this . expireAt = expireAt ; this . server = server ; this . world = world ; this . contexts = contexts == null ? ContextSet . empty ( ) : contexts . makeImmutable ( ) ; }
target:  Make an immutable node instance