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What are Chained Exceptions ?
The chained exception feature allows you to associate another exception with an exception. This second exception describes the cause of the first exception. Lets take a simple example. You are trying to read a number from the disk and using it to divide a number. Think the method throws an ArithmeticException because of an attempt to divide by zero (number we got). However, the problem was that an I/O error occurred, which caused the divisor to be set improperly (set to zero). Although the method must certainly throw an ArithmeticException, since that is the error that occurred, you might also want to let the calling code know that the underlying cause was an I/O error. This is the place where chained exceptions come in to picture.
Throwable getCause( )
Throwable initCause(Throwable causeExc)
Is it necessary that each try block must be followed by a catch block ?
It is not necessary that each try block must be followed by a catch block. It should be followed by either a catch block OR a finally block. And whatever exceptions are likely to be thrown should be declared in the throws clause of the method.
If I write return at the end of the try block, will the finally block still execute ?
Yes even if you write return as the last statement in the try block and no exception occurs, the finally block will execute. The finally block will execute and then the control return.
If I write System.exit (0); at the end of the try block, will the finally block still execute ?
No in this case the finally block will not execute because when you say System.exit (0); the control immediately goes out of the program, and thus finally never executes.
What are Checked and UnChecked Exception ?
A checked exception is some subclass of Exception (or Exception itself), excluding class RuntimeException and its subclasses.
Making an exception checked forces client programmers to deal with the possibility that the exception will be thrown. eg, IOException thrown by java.io.FileInputStream’s read() method·
Unchecked exceptions are RuntimeException and any of its subclasses. Class Error and its subclasses also are unchecked. 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.
Give me some examples of Checked Exceptions and Unchecked Exceptions ?
Unchecked Exceptions.
ArithmeticException
ArrayIndexOutOfBoundsException
ClassCastException
IndexOutOfBoundsException
IllegalStateException
NullPointerException
SecurityException
Checked Exception
ClassNotFoundException
CloneNotSupportedException
IllegalAccessException
InstantiationException
InterruptedException
NoSuchFieldException
NoSuchMethodException
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