Exception Handling in Java

Exception Handling in Java

• An exception in programming is an event that occurs during the execution of a program that disrupts the normal flow of instructions.
• In languages without exception handling, errors are typically managed by returning error codes or flags.
• Java provides a built-in exception handling mechanism using try-catch blocks to handle errors.

Throwing Exceptions

• To 'throw' an exception in Java means to signal that an error has occurred.
• Checked exceptions are used to violate the rules of the Java language or execution environment.
• Manually generated exceptions are typically used to indicate a logical error in the program.

Exception Handling Constructs

• The throw keyword is used to throw a specific exception from the program.
• The main benefit of exception handling in Java is to allow for more robust and fault-tolerant programs.
• Checked exceptions are specified within a method using the throws keyword.
• The IOException class is the most general class representing any type of I/O error in Java.

Exception Handling Theory

• The "termination" model of exception handling theory implies that the error is so critical that there's no way to recover from it.

Try-Catch Blocks

• The finally clause specifies any code that must be executed whether or not an exception occurs.
• The throws clause specifies the exceptions that a method can throw.
• The purpose of the catch clause is to handle the exception that has been thrown.
• Separating error-handling code from 'regular' business logic code is beneficial in Java as it allows for more modular and reusable code.

Multi-Threading

• One difference between process-based multi-tasking and thread-based multi-tasking is that processes are heavyweight, whereas threads are lightweight.
• A characteristic of threads in thread-based multi-tasking is that they share the same memory space.
• Inter-process communication is considered expensive in process-based multi-tasking because it requires a lot of overhead in terms of memory and resources.
• One reason for using multi-threading in programming is to improve the responsiveness of a program.

Thread Lifecycle

• A thread is different from a process in that it is a separate path of execution within a process.
• A significant advantage of thread-based multi-tasking over process-based multi-tasking is that it is more efficient in terms of memory and resources.
• The start method is used to initiate the execution of a thread.
• After the creation of a Thread instance but before the start() method invocation, the thread is in the "Newborn" state.
• The join method is used to wait for a thread to terminate.
• The Runnable interface is used to create a new thread.
• The Dead state signifies that a thread has completed its execution and can no longer be run.
• A thread enters the "Runnable" (Ready-to-run) state when it is ready to be executed by the thread scheduler.
• The sleep method is used to pause the execution of a thread for a specified period of time.
• The join method is used to wait for a thread to terminate.
• The Running state signifies that a thread is currently executing its code.
• When a thread completes its run method, it enters the "Dead" state.