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|What is the difference between error and an exception?|
|An error is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. These JVM errors and you can not repair them at runtime. While exceptions are conditions that occur because of bad input etc. e.g. FileNotFoundException will be thrown if the specified file does not exist. Or a NullPointerException will take place if you try using a null reference. In most of the cases it is possible to recover from an exception (probably by giving user a feedback for entering proper values etc.).|
|How to create custom exceptions?|
|Your class should extend class Exception, or some more specific type thereof.|
|If I want an object of my class to be thrown as an exception object, what should I do?|
|The class should extend from Exception class. Or you can extend your class from some more precise exception type also.|
|If my class already extends from some other class what should I do if I want an instance of my class to be thrown as an exception object?|
|One can not do anytihng in this scenarion. Because Java does not allow multiple inheritance and does not provide any exception interface as well.|
|How does an exception permeate through the code?|
|An unhandled exception moves up the method stack in search of a matching When an exception is thrown from a code which is wrapped in a try block followed by one or more catch blocks, a search is made for matching catch block. If a matching type is found then that block will be invoked. If a matching type is not found then the exception moves up the method stack and reaches the caller method. Same procedure is repeated if the caller method is included in a try catch block. This process continues until a catch block handling the appropriate type of exception is found. If it does not find such a block then finally the program terminates.|
|What are the different ways to handle exceptions?|
|There are two ways to handle exceptions, 1. By wrapping the desired code in a try block followed by a catch block to catch the exceptions. 2. List the desired exceptions in the throws clause of the method and let the caller of the method hadle those exceptions. What is the basic difference between the 2 approaches to exception handling. 1> try catch block 2> specifying the candidate exceptions in the throws clause|
|When should you use which approach?|
|In the first approach as a programmer of the method, you yourself are dealing with the exception. This is fine if you are in a best position to decide should be done in case of an exception. Whereas if it is not the responsibility of the method to deal with it's own exceptions, then do not use this approach. In this case use the second approach. In the second approach we are forcing the caller of the method to catch the exceptions, that the method is likely to throw. This is often the approach library creators use. They list the exception in the throws clause and we must catch them. You will find the same approach throughout the java libraries we use.|
|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.|
|How are Observer and Observable used?|
|Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.|
|What is synchronization and why is it important?|
|With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.|
|How does Java handle integer overflows and underflows?|
|It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.|
|Does garbage collection guarantee that a program will not run out of memory?|
|Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection|
|What is the difference between preemptive scheduling and time slicing?|
|Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.|
|When a thread is created and started, what is its initial state?|
|A thread is in the ready state after it has been created and started.|
|What is the purpose of finalization?|
|The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.|
|What is the Locale class?|
|The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.|
|What is the difference between a while statement and a do statement?|
|A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once.|
|What is the difference between static and non-static variables?|
|A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.|
|How are this() and super() used with constructors?|
|This() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.|
|What are synchronized methods and synchronized statements?|
|Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.|
|What is daemon thread and which method is used to create the daemon thread?|
|Daemon thread is a low priority thread which runs intermittently in the back ground doing the garbage collection operation for the java runtime system. setDaemon method is used to create a daemon thread.|
|Can applets communicate with each other?|
|At this point in time applets may communicate with other applets running in the same virtual machine. If the applets are of the same class, they can communicate via shared static variables. If the applets are of different classes, then each will need a reference to the same class with static variables. In any case the basic idea is to pass the information back and forth through a static variable. An applet can also get references to all other applets on the same page using the getApplets() method of java.applet.AppletContext. Once you get the reference to an applet, you can communicate with it by using its public members. It is conceivable to have applets in different virtual machines that talk to a server somewhere on the Internet and store any data that needs to be serialized there. Then, when another applet needs this data, it could connect to this same server. Implementing this is non-trivial.|
|How does a try statement determine which catch clause should be used to handle an exception?|
|When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exceptionis executed. The remaining catch clauses are ignored.|
What is the value of cot 4π/3 ?
Article-24 of the Indian Constitution ‘Prohibition of employment of children in factories, etc’ deals with?
Article-134A of the Indian Constitution ‘Certificate for appeal to the Supreme Court’ deals with?
Who invented Aspirin?
A larger force on a rotating body results in larger?
What is the unit of the physical quantity, magnetic flux density?
The system of equations 2x + 4y = 6 and 4x + 8y = 8 is ?
|Time and Distance|
A thief is spotted by a policeman from a distacne of 100 m. When the policeman starts the chase, the thief also starts running. If the speed of the theif is 8 km / hour and that of the policeman is 10 km/hour, then how far will the theif have to run before he is overtaken?
Aman and Alok attempted to solve a quadratic equation. Aman made a mistake in writing down the constant term and ended up in roots (4, 3). Alok made a mistake in writing down the coefficient of x to get roots (3, 2). The correct roots of the equation are?
The effective annual rate of interest corresponding to a nominal rate of 22% per annum payable half-yearly is?
|Volume and Surface Area|
If the volume of a cylinder is 2156 cubic cm and height is 14 cm, find its radius?
What is the equation of the line which passes through the points (2, 3) and (- 4, 1)?
In △ABC, the angle bisector of ∠A cuts BC at E. Find length of AC, if lengths of AB, BE and EC are 9 cm, 3.6 cm and 2.4 cm?
In a triangle, the length of the opposite side of the angle which measures 45° is 8√2 cm, what is the length of the side opposite to the angle which measures 90°?
|General Knowledge of India|
The boundary line between India and Pakistan is called?
Which city is located on the banks of the river Mahanadi?
When was the battle of Haldighati fought?
In 1498, which Portuguese explorer discovered a new sea route from Europe to India?
|General Knowledge of India|
Chapchar Kut is a festival of which State?
In chemistry, soap is a salt of a ?
Which of the following is a Direct tax?
Sauria lacertidae is the scientific name of?
Which of the following is a primary function of haemoglobin?
A factory buys 8 machines.3 Machine A, 2 Machine B and rest Machine C. Prices of the machines are 100000, 80000 and 45000 respectively.Calculate the average cost of these machines?
Ticket for an adult is 500 and a child is 200. 1 child goes free with two adults. If a group has 20 adults and 8 children what will be the discount the group get?