Common Java Errors and How to Fix Them
Browse all documented Java errors with detailed explanations, root causes, and step-by-step fixes.
Cannot find symbol: method get(int) in class java.util.ArrayList
This error occurs when the Java compiler cannot find a method declaration in the class or interface that you are trying …
Cannot execute query. The database has been closed.
This error occurs when you attempt to execute a database query after closing the database connection.…
Cannot find symbol: variable 'username' on line 17
This error occurs when Java cannot find the declaration of a variable, method, or class. It is often caused by a typo or…
Invalid data type: org.hibernate.HibernateException: No Dialect class marked wit
This error occurs when Hibernate, a popular Java ORM library, fails to find the correct dialect for a database. A dialec…
Cannot instantiate interface: org.springframework.web.servlet.view.JstlView
This error occurs when attempting to instantiate a non-abstract class that is an interface, which is not allowed in Java…
You cannot use a scrollable result set with a Statement object that has been set
This error occurs when you attempt to use a Statement object to scroll through a result set after it has been set to be …
java.sql.SQLException: Column 'username' is either not in any table in the FROM
This error occurs when the database connection is unable to execute a SQL query due to an invalid or incorrect query syn…
No qualifying bean of type 'com.example.data.DataSource' available
This error occurs when the Spring Framework is unable to find a bean that matches the specified type in the application …
Method call expected here for 'continue' statement. Use 'continue' with a label
The 'continue' statement in Java is used to skip the current iteration and move to the next one in a loop. However, if i…
The SQL syntax error or exception 'ORA-01722: invalid number' occurred while exe
This error is thrown when the database encounters an invalid number while executing a SQL query. This can happen when th…
Cannot find symbol: variable 'result' in class 'Main'
This error occurs when the Java compiler is unable to find a variable, method, or class that is being used. It's a commo…
Cannot serialize instance of com.mysql.cj.jdbc.NonTransientConnectionException:
This error occurs when the Java application is unable to acquire a connection to the database, often due to a high load …
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