question: public static boolean expressionIsValidSQl ( String filter ) { if ( filter == null ) { return true ; } if ( TextUtils . containsAnyIgnoreCase ( filter , ILLEGAL_SQL_KEYWORDS ) ) { return false ; } for ( int i = 0 ; i < filter . length ( ) ; i ++ ) { char ch = filter . charAt ( i ) ; if ( ! ( Character . isWhitespace ( ch ) || Character . isLetterOrDigit ( ch ) || SQL_VALID_CHARS . contains ( ch ) ) ) { return false ; } } return true ; }
target:  Validates whether a filter expression contains malicious code such as SQL injection attempts.