Examples of java

Answer 1

The term "exception" means "exceptional condition" and is an occurrence that alters the normal program flow. A bunch of things can lead to exceptions, including hardware failures, resource exhaustion, and good old bugs. When an exceptional event occurs in Java, an exception is said to be "thrown." The code that's responsible for doing something about the exception is called an "exception handler," and it "catches and handles" the thrown exception.

Exception handling works by transferring the execution of a program to an appropriate exception handler when an exception occurs. For ex: Your website displays the users bank account details. Suddenly if the bank database is down, imaging how the user would feel if an abrupt error page with numerous lines of java exception messages spewed all over the screen? First of all, it would be embarrassing and second of all, the user will get annoyed. Instead, if your code catches this database down scenario and displays a graceful message on screen saying "We are currently experiencing some difficulties in our system. Kindly try after some time. Thank you" it would be much better isnt it? That is exactly why we have or rather why we need Exception Handling.

Answer 2

//A simple "Hello World" program. If you would like something longer or more complicated, leave a //comment.

public class HelloWorld{

public static void main(String []args){

System.out.println("Hello World!");

}

}

Answer 3

Thrown when a thread is waiting, sleeping, or otherwise paused for a long time and another thread interrupts it using the interrupt method in class Thread. Thrown when a thread is waiting, sleeping, or otherwise occupied, and the thread is interrupted, either before or during the activity. Occasionally a method may wish to test whether the current thread has been interrupted, and if so, to immediately throw this exception. The following code can be used to achieve this effect: if (Thread.interrupted()) // Clears interrupted status! throw new InterruptedException(); Every thread has a Boolean property associated with it that represents its interrupted status. The interrupted status is initially false; when a thread is interrupted by some other thread through a call to Thread.interrupt(), one of two things happens. If that thread is executing a low-level interruptible blocking method like Thread.sleep(), Thread.join(), or Object.wait(), it unblocks and throws InterruptedException. Otherwise, interrupt() merely sets the thread's interruption status. Code running in the interrupted thread can later poll the interrupted status to see if it has been requested to stop what it is doing; the interrupted status can be read with Thread.isInterrupted() and can be read and cleared in a single operation with the poorly named Thread.interrupted(). Interruption is a cooperative mechanism. When one thread interrupts another, the interrupted thread does not necessarily stop what it is doing immediately. Instead, interruption is a way of politely asking another thread to stop what it is doing if it wants to, at its convenience. Some methods, like Thread.sleep(), take this request seriously, but methods are not required to pay attention to interruption. Methods that do not block but that still may take a long time to execute can respect requests for interruption by polling the interrupted status and return early if interrupted. You are free to ignore an interruption request, but doing so may compromise responsiveness. One of the benefits of the cooperative nature of interruption is that it provides more flexibility for safely constructing cancelable activities. We rarely want an activity to stop immediately; program data structures could be left in an inconsistent state if the activity were canceled mid-update. Interruption allows a cancelable activity to clean up any work in progress, restore invariants, notify other activities of the cancellation, and then terminate. Dealing with InterruptedException If throwing InterruptedException means that a method is a blocking method, then calling a blocking method means that your method is a blocking method too, and you should have a strategy for dealing with InterruptedException. Often the easiest strategy is to throw InterruptedException yourself, as shown in the putTask() and getTask() methods in Listing 1. Doing so makes your method responsive to interruption as well and often requires nothing more than adding InterruptedException to your throws clause.