#fixed code
                                public boolean execute(String sql) throws SQLException {
        internalClose();

        SQLExtension ext = ExtendedCommand.parse(sql);
        if (ext != null) { 
            ext.execute(db);

            return false;
        }

        this.sql = sql;

        db.prepare(this);
        return exec();
    }
#vulnerable code 
                                public boolean execute(String sql) throws SQLException {
        internalClose();

        SQLExtension ext = ExtendedCommand.parse(sql);
        if (ext != null) { 
            ext.execute(db);

            return false;
        }

        this.sql = sql;

        boolean success = false;
        try {
            db.prepare(this);
            final boolean result = exec();
            success = true;
            return result;
        } finally {
            if (!success) {
                internalClose();
            }
        }
    } 
                            #location 2 
                            #vulnerability type THREAD_SAFETY_VIOLATION