Question

What is the use of rethrowing checked and unchecked exceptions?

Answer 1

If you want to execute some code when a problem happens without hiding the problem.

For example, let’s say you want to rollback changes if an exception occurs while writing to a database:

try {
    writeToDatabase();
} catch(Exception ex) {
    rollbackChanges();
}

If you use this code, the calling function will never find out that an exception occurred.

Instead, you should write

try {
    writeToDatabase();
} catch(Exception ex) {
    rollbackChanges();
    throw ex;
}