What are Checked and Unchecked exception ?

• A Checked exception is some subclass of Exception (or Exception itself), excluding class RuntimeException and its subclasses.
• Unchecked exceptions are RuntimeException and any of its subclasses. Class Error and its subclasses also are unchecked.

• Making a checked exception forces client programmers to deal with the possibility that the exception will be thrown. eg, IOException thrown by java.io.FileInputStream's read() method.
• With an unchecked exception, however, the compiler doesn't force client programmers either to catch the exception or declare it in a throws clause. In fact, client programmers may not even know that the exception could be thrown. eg, StringIndexOutOfBoundsException thrown by String's charAt() method.

• Checked exceptions must be caught at compile time.
• Runtime exceptions do not need to be, Errors often cannot be.