Java Exception Handling and Syntax

• An exception can be anything that interrupts the normal flow of the program.
• When an exception occurs program processing gets terminated and doesn't continue further.
• In such cases we get a system-generated error message.
• Exception can occur at runtime.
• Reasons for Exceptions can include opening a non-existing file, network connection problem, class file missing which was supposed to be loaded, etc.
• The difference between error and exception is that errors indicate serious problems and abnormal conditions that most applications should not try to handle, while exceptions are conditions within the code.
• To terminate the program normally and to give a user-friendly error message to the user we have to handle the exceptions.
• Exception handling using a try…catch block is the way to do this.
• A try block must be followed by a catch block, or finally block, or both.
• A catch block associated with a try block executes if an exception of a particular type occurs within the try block.
• The syntax of try catch in Java is as follows:
• try { //statements that may cause an exception } catch (exception_type) { //error handling code }
• The flow of a try catch block is as follows:
• If an exception occurs in try block, the control of execution is passed to the catch block from try block.
• The exception is caught up by the corresponding catch block.
• If the try block is not throwing any exception, the catch block will be completely ignored and the program continues.
• If the try block throws an exception, the appropriate catch block (if one exists) will catch it.
• All the statements in the catch block will be executed.
• System generated exceptions are automatically thrown by the Java run time system. To manually throw an exception, we use the keyword throw.
• Since exceptions in Java are type of Throwable, all Java methods use throw statement to throw an exception.
• The throw statements required Throwable objects.
• The exception class is the base class for all exception classes.
• Types of Exceptions include checked exceptions (those that extend the Throwable class) and unchecked exceptions (those that extend RuntimeException).
• It is important to declare any exceptions that a method might throw in the throws clause of the method if the compiler has been configured to check for them.
• A try block can be followed by multiple catch blocks.
• Each catch block must contain a different exception handler.
• If an exception occurs in the try block then an exception is passed to the first catch block in the list.
• If an exception type matches with the first catch block it gets caught, if not the exception is passed down to the next catch block.
• The finally block in Java is used to put important codes such as clean up code.
• The finally block executes whether exception rise or not and whether exception handled or not.
• A finally contains all the crucial statements regardless of the exception occurs or not.

Learn about the concepts of exception handling in Java, including the difference between errors and exceptions, syntax for try...catch blocks, throwing exceptions, types of exceptions, declaring and using multiple catch blocks, and the importance and usage of the finally block.