Throw Exception In Overridden Method

Mar 19, 2015

I am practicing OCPJP ....

import java.lang.*;
class InvalidValueException extends IllegalArgumentException {}
class InvalidKeyException extends IllegalArgumentException {}
class BaseClass {
void foo() throws IllegalArgumentException {
throw new IllegalArgumentException();

[Code] .....

Which one of the following options correctly describes the behavior of this program? And the answer is (definitely) --> The program will print : InvalidKeyException exception, but when i saw the explanation, it tells

It is not necessary to provide an Exception thrown by a method when the method is overriding a method defined with an exception (using the throws clause).

I don't know, but i think it will compiled because the Exception that is thrown by the foo method in DeriDeri class is inherited from unchecked exception.. so it is not necessary to declare throws statement on its method.. and if the exception was checked exception the answer must be different right?

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if(c.check()== true)
{
Menu start = new Menu(c.getID());
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[code].....

I get an error "unreported exception java.SQLException; must be caught or declared to be thrown" how can i solve this I have taken a few basic classes but never got to exceptions.

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Many of them inherit from common exceptions, so I've been tempted to throw the parent classes. But I've quickly discarded that option because I've read that it's a bad practice, since a method may throw only a subset of the children of that parent class, not all.

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For starters here is my code:

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int x=5;
}
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}
public class CovariantTest {
public A getObject() {

[Code] ....

And this is the output I get:

sub
5

I am unable to figure out how this is outputting 5 instead of 6. The getObject method of SubCovariantTest is obviously the one being called, and it returns a new B(). So why am I getting class A's x value? I thought since I was getting a B object returned that I would get B's x value.

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"up" is basically a text Button:

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is this true? maybe i'm misunderstanding it, but i thought the JVM looks at the object at run time and checks the object type. the context of the quote is about checked exceptions, but it seems like the statement should stand regardless of context. but this doesn't back up my experience. for example:

public class Test{
public void print(){
System.out.println("Super");
} public static void main(String[] args){
Test t = new SubTest();

[Code] ....

Will invoke the subclass method. like i said, maybe i'm missing something.

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I don't understand, why when in the constructor of the superclass A the method init() is called (line 4), the overridden version of the subclass is invoked (line 26) and not the superclass version (line 7):

class A {
public A () {
init();
}
public void init() {
System.out.println("test");

[Code] ....

I would have guessed that above code prints

test
1

But instead you get a NPE (because when the constructor of B is invoked

public static void main(String[] args) {
new B();
}

Then there is first the implicit call to super:

public B() {
s = " ";
init();
}

Which is the constructor of A:

public A () {
init();
}

But here now this init() method is not the version of A ( public void init() {
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}) but the overriden version of the subclass (B): public void init() {
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Here is where I created the exception that receives a string consisting of ID and wage.

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public EmployeeException(String Employee)
{
super(Employee);
}
}

Here is where I created the Employee class with the two fields. I also believe I am throwing the exception if the hourly wage is < $6 or > $50.

public class Employee
{
int idNum;
double hourlyWage; 
public void Employee(int empID, double empWage) throws EmployeeException
{
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[Code]...

Now, I need to write an application with three employees and display a message when an employee is successfully created or not. This is what I have so far... I'm trying to get it to work with one employee, and then I can easily go back and add two more.

import javax.swing.*;
public class ThrowEmployee
{
public static void main (String[] args)
{
try
{
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}
 
[Code

The current compile error that I'm receiving is: ThrowEmployee.java:12: error: constructor Employee in class Employee cannot be applied to given types;

Employee one = new Employee(542, 15.20);
^
required: no arguments
found: int,double
reason: actual and formal argument lists differ in length
1 error

I have public void Employee(int empID, double empWage) in my Employee class, so why is it saying that no arguments are required? Not sure if I'm missing a step with throwing exceptions, because this error has always been a simple fix when I've come across it in the past?!?

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Snippet of my code:

import java.io.*;
import java.util.*;
public class Customer {
private String lastName;
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[Code] .....

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at java.util.Scanner.<init>(Scanner.java:611)
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