question: private static int system_depth ( Stack < SootMethod > stack ) { for ( int ii = stack . size ( ) - 1 ; ii > 0 ; ii -- ) { SootMethod m = stack . get ( ii ) ; if ( ! is_system ( m ) ) return stack . size ( ) - ii ; } return stack . size ( ) ; }
target:  Returns the number of calls back to the last non-system call 