报错信息: java.sql.SQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '?' at line 1 at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:120) at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) at com.mysql.cj.jdbc.StatementImpl.executeQuery(StatementImpl.java:1200) at PreparedStatement.main(PreparedStatement.java:21) Exception in thread "main" java.lang.NullPointerException at PreparedStatement.main(PreparedStatement.java:30)