Java Questions

[PugoOfficial]

I'm asking here because I can't find it on Google on what codes/types are they

Q1:is the type of exception thrown when a application stops running before its natural end.
Q2:User Exceptions are exceptions that are manually thrown by the programmer using what?
Q3:can the 'trycatch' block be nested?
LastQ: Can Exceptions be generated through methods calls? if not .. what can?

Thanks in Advance for those who can answer

[Ivyk]

Not trying to be an asshole but it looks like an assignment or homework maybe it is maybe it isn't, is it?

[PugoOfficial]

Not trying to be an asshole but it looks like an assignment or homework maybe it is maybe it isn't, is it?

Honestly, there the questions in an exam I'm about to take that I can't find the answers for. If you can't help I understand it's kind of cheating i know but I would want to get a higher grade

[Guest]

The answer to question 3 is yes. The other questions do not make sense.

1. Exceptions can't be thrown after a program stops running. And any type of exception may cause a program to stop execution if it is not caught. This question makes no sense.
2. Exceptions are thrown, period, not "by" anything. This questions makes no sense.
3. Sure. It is usually an bad way of doing things, though.
4. Exceptions can be "thrown" in a method, I guess that is the same thing as "generated"? This question doesn't make any sense, either.

Good luck with your cheating.

[msvelev]

I don't consider that cheating.. He's just asking questions before a test, that's normal. However as @SSL said q1/2 make no sense, agree with him on q3 and about q4... Please do some simple main methods in which you throw exceptions so you Can understand them better. I'm on a mobile device right now so I can't write full examples but consider something like :

System.out.orintln("1");

throw new RuntimeException();

System.out.println("2");

And see what your compiler will tell you.

Also you can write a program which does the same but uses a random generator and throws the exception 50 percent of the time. I think those two will help you understand better how exceptions work.

[Tirant]

I think he's talking about RuntimeExceptions, which don't have to be caught by the compiler (like ArrayIndexOutOfBoundsException) and are thrown at run time.

 

User exceptions could be like:

public int addPositiveNumbers(int x, int y) {

if (x < 0 || y < 0) {

throw new InvalidArgumentException();

}

 

return x + y;

}

 

Stupid question, but he's probably looking for the "throw" keyword. You should also know what "throws" means (Hint: it's not used within a method call).

 

try {

} catch()

 

blocks can be nested. I did it on a regular basis to tie up files. Usually you try { open file } catch( some error ) { } finally { close file/release resources }. This is a bit different now since many Java classes include "closable" interface which means it will release the resources for you... try (BufferedReader reader = new BufferedReader(...)) { reader.readLine()... }

 

I don't understand your last question: Can Exceptions be generated through methods calls? if not .. what can?

Is he talking about exception propagation, i.e., if an exception is thrown by a method, it is passed back up the stack until it reaches your original method call, where you need to catch and address it? If so, then yes: exception propagation. Else I don't know what the hell he's talking about.

[brandishwar]

I'm asking here because I can't find it on Google on what codes/types are they

Q1:is the type of exception thrown when a application stops running before its natural end.

Q2:User Exceptions are exceptions that are manually thrown by the programmer using what?

Q3:can the 'trycatch' block be nested?

LastQ: Can Exceptions be generated through methods calls? if not .. what can?

Thanks in Advance for those who can answer

 

1. An exception that causes an application to stop running before it's normal end is an uncaught runtime exception.

 

2. Typically: throw new ExceptionClass; where ExceptionClass is a class derived from the Exception class.

 

3. Try/catch blocks can be nested, but each try must have either a catch or finally block with it.

 

4. There are exceptions that can be generated through method calls, and these would be due to incompatibilities between jars within the classpath. An example is the ClassNotFoundException exception.