Java Exceptions
What are the different ways to handle exceptions?
Nov 26th
There are two ways to handle exceptions: • Wrapping the desired code in a try block followed by a catch block to catch the exceptions. • List the desired exceptions in the throws clause of the method and let the caller of the method handle those exceptions.
Can we have the try block without catch block?
Nov 26th
Yes, we can have the try block without catch block, but finally block should follow the try block. Note: It is not valid to use a try clause without either a catch clause or a finally clause.
How to create custom exceptions?
Nov 26th
By extending the Exception class or one of its subclasses. Example:
class MyException extends Exception { public MyException() { super(); } public MyException(String s) { super(s); } }
What if there is a break or return statement in try block followed by finally block?
Nov 26th
If there is a return statement in the try block, the finally block executes right after the return statement encountered, and before the return executes.
Why Errors are Not Checked?
Nov 26th
A unchecked exception classes which are the error classes (Error and its subclasses) are exempted from compile-time checking because they can occur at many points in the program and recovery from them is difficult or impossible. A program declaring such exceptions would be pointlessly.
Why Runtime Exceptions are Not Checked?
Nov 26th
The runtime exception classes (RuntimeException and its subclasses) are exempted from compile-time checking because, in the judgment of the designers of the Java programming language, having to declare such exceptions would not aid significantly in establishing the correctness of programs. Many of the operations and constructs of the Java programming language can result in runtime exceptions. The information available to a compiler, and the level of analysis the compiler performs, are usually not sufficient to establish that such run-time exceptions cannot occur, even though this may be obvious to the programmer. Requiring such exception classes to be declared would simply be an More >
What is the use of finally block?
Nov 26th
The finally block encloses code that is always executed at some point after the try block, whether an exception was thrown or not. This is right place to close files, release your network sockets, connections, and perform any other cleanup your code requires.
Note: If the try block executes with no exceptions, the finally block is executed immediately after the try block completes. It there was an exception thrown, the finally block executes immediately after the proper catch block completes
Which is superclass of Exception?
Nov 26th
“Throwable”, the parent class of all exception related classes.
What are the advantages of using exception handling?
Nov 26th
Exception handling provides the following advantages over “traditional” error management techniques:
- Separating Error Handling Code from “Regular” Code.
- Propagating Errors Up the Call Stack.
Grouping Error Types and Error Differentiation.
What are the types of Exceptions in Java
Nov 26th
There are two types of exceptions in Java, unchecked exceptions and checked exceptions.
- Checked exceptions: A checked exception is some subclass of Exception (or Exception itself), excluding class RuntimeException and its subclasses. Each method must either handle all checked exceptions by supplying a catch clause or list each unhandled checked exception as a thrown exception.
Unchecked exceptions: All Exceptions that extend the RuntimeException class are unchecked exceptions. Class Error and its subclasses also are unchecked.
