Java provides a hierarchy of classes that represent different kinds of exceptions. These classes are rooted in the java.lang package’s Throwable class, along with its Exception, RuntimeException ...

A good example would be the FileNotFoundException. This does exactly what it says on the tin: this exception is “thrown” when Java looks for a particular file and can’t find it.

In Java, exceptions are one of many structures that govern the control flow of a program. Specifically, they are unintended side effects of a program's normal execution.