I believe that when we do the project, the console box often appear a variety of anomalies, a long time, you will find common also a few, below I summarize the common anomalies for your reference.
1 Java.lang.UnsupportedClassVersionError
Literally we can see that the class version does not support the error, in other words, the JDK version is incompatible, because we compiled the class on the high version, run in the lower version of the JVM, this is the answer I searched. It's okay to understand. But I found that my myeclipse is a high version of the JDK, the introduction of the project is a low version, it should be supported, but the same error occurred, so it is not easy to understand that the low version does not support the high version of the problem, the high version may not be compatible with the lower version, so it is best to set the same JDK , including project references and the JDK referenced by Tomcat.
2 java.lang.NullPointerException
This is a null pointer exception, which means that the object you are calling is NULL or the value is empty, the object is empty, and it is possible that you are referencing the object's method when there is no new object.
3 arrayindexoutofboundsexception
Array subscript out-of-bounds exception that is thrown when an index value that accesses a sequence is less than 0 or greater than or equal to the sequence size.
4 FileNotFoundException
The file did not find an exception that was thrown when an attempt was made to refer to a file under a path without a file under that path.
5 NumberFormatException
A numeric format exception that is thrown when an attempt is made to convert a string to a specified numeric type that does not satisfy the format required by the number type.
6 SQLException
Database operation exception, generally because the SQL statement is not correct, so that we write SQL statements is the best way to run the database command first.
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Common exceptions in Java project development
