Basis For Making Exception As Checked Or Unchecked
Oct 10, 2014
I know checked exception need to be checked at compile time and runtime exception need not be checked at compile time.
My question is not related to the definition.
The question is on what basis have they selected that FileNotFound exception is a checked exception and NullPointerException is an unchecked exception? Is it the random wish of the creator or is there reason behind why something is selected as checked exception and something as unchecked?
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Mar 11, 2014
what is the use of checked exception.I know unchecked exception or Runtime exception are thrown by jvm whenever programmer makes any mistake in logic and current thread is terminated.But checked Exception are checked at compile time so that compiler compels programmer to put risky methods in try catch clause. And this checked Exception are caused due to problem in IO operation or any such operation which the programmer can't control.Programmer can't do anything to avoid this checked exception but can catch this exception.
Now the question is Why compiler compels checked exception to be put in try catch clause but doesn't complain anything in case of Runtime Exception???
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Sep 24, 2014
I am making an expert system using Jess about animals. I wanted to make an interface using Swing and so I did. I have a problem using group layouts. The application works fine but at the end a exceptions is thrown:
Exception in thread "AWT-EventQueue-0" java.lang.IllegalStateException: javax.swing.JLabel[,0,0,0x0,invalid,alignmentX=0.0,
alignmentY=0.0,border=,flags=8388608,maximumSize=,minimumSize=,
preferredSize=,defaultIcon=,disabledIcon=,horizontalAlignment=LEADING,
horizontalTextPosition=TRAILING,iconTextGap=4,labelFor=,
text=The animal is a cheetah.,verticalAlignment=CENTER,
verticalTextPosition=CENTER] is not attached to a horizontal group
[Code] ....
The application ask the user some questions about the animal. When the expert system has enough information to know the animal it tells the name of the animal and shows a picture of it. The exception is thrown when the application has guessed the animal and shows the response.
Here is the code:
package xindria;
import javax.imageio.ImageIO;
import javax.swing.*;
import javax.swing.GroupLayout.SequentialGroup;
import java.awt.*;
import java.awt.event.ActionEvent;
[Code] .....
I think the problem is related to the group layouts. I will attach the eclipse project too...
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Jun 15, 2014
Check out the following basic code (assume that dog has a method called bark):
Dog d = new Dog();
Object o = d;
o.bark(); // error
But why? Isn't o just a pointer to a memory address which has the dog object? If so, why can't the compiler see that the object has a method called bark? Or, to ask the question another way, why is Java designed to check the object reference to see if the method exists instead of the object itself?
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Sep 25, 2014
I want to read this csv file and store contents on column basis; as date (single array) for all dates. open, high, low and close and be able to manipulate individual elements of the array such as Sum += close[i];
public void pratice() throws Exception {
// Create a File instance
BufferedReader br=new BufferedReader(new FileReader("gtk.csv"));
content = new String[1000];
while(content !=null) {
content[++count] = br.readLine();
[Code] .....
the file looks like this
date Open high low close
12-12-2011 15.00 15.40 14.5 15.2
11-12-2011 15.02 15.70 14.9 15.00
10-12-2011 14.70 16.00 14.70 15.02
...
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Sep 30, 2014
Hospital management system in java. I have designed Hospital, Doctor, Patient, Appointment classes. I am able to add doctor list and patient list and show the doctor list and patient list. How to take new appointment from a patient and assign it to a particular doctor and how to generate a report for inpatient and outpatient on a daily basis.
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Jun 30, 2014
String filename="C:UsersRajashekarDesktopfwfwdSoftware Failures1_Test.txt";//Input Files
String data;
public ArrayList<String> value=new ArrayList<String>();
public void read() throws IOException{
File f = new File(filename);
[Code] ....
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Jul 15, 2014
There is a sentence in JLS 7 which I can't figure it out. It says :
A cast from a type S to a parameterized type T is unchecked unless at least one of the following conditions holds:
-S <: T
-All of the type arguments (§4.5.1) of T are unbounded wildcards
-T <: S and S has no subtype X other than T where the type arguments of X are not contained in the type arguments of T.
Condition one and two I got it. But the number three is really bugging me. I write some code in order to try to understand it.
class G<X>{}
class D<T,U> extends G<T>{}
G<String> g = new G<>();
D<String, Integer> dd = (D<String, Integer>) g;
In Eclipse I got no warning but it shouldn't give one ?
Because g has others subtypes than D<String, Integer> (e.g. D<String, List> , D<String, G>)
Am I missing something about the contained type arguments ?
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Feb 28, 2014
I am getting "Type safety: Unchecked cast from Object to LinkedList<EventData>" in eclipse for a piece of code stated below
public LinkedList<EventData> loadFromFile(File file) {
queue=new LinkedList<EventData>();
//Some piece of code
return (LinkedList<EventData>)queue.clone(); //--->getting warning here
}
I know that because clone() method is returning Object, hence compiler doesn't have type information that's why showing warning. I don't want to suppress this warning instead i want to fix it.
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Jan 24, 2014
I was giving a quick skim to some tutorials on the internet where I have found the exception that is handled is also declared in the throws clause of the method wrapping the try-catch block. For a code representation consider the following:
public void methodName() throws IOException {
try {
...
} catch (IOException ex) {
.... TODO handle exception
}
}
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Sep 29, 2014
Right, so I got this program. It takes input from the user and assigns it to fields on an object. But, it's meant to check the users input. If the user enters bad input, it's supposed to throw this exception. For each of these exceptions, theres a class specifically for it.
public class PayrollDemo
{
public static void main(String[] args)
{
Payroll pr = new Payroll ("Test Name", 234);
System.out.println("Current Employee Information.
");
System.out.println("Name: " + pr.getName());
System.out.println("ID: " + pr.getID());
System.out.println("Hourly Pay Rate: " + pr.getHourlyPayRate());
[Code] ....
And this is the exception class.
public class InvalidNameException extends Exception
{
/**
No-arg constructor
*/
public InvalidNameException()
{
super("Invalid name");
}
}
PayrollDemo.java:43: error: cannot find symbol
InvalidNameException.InvalidNameException();
^
symbol: method InvalidNameException()
location: class InvalidNameException
1 error
It's just meant to tell the user that they entered an invalid value, which would mean if they entered an empty string instead of a name.
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May 30, 2006
how this is done using session.setMaxInactiveInterval(); at first, i did not set anything but it expires anyway.so i'm trying not to let the session expire.session.setMaxInactiveInterval(0) does not work.
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Sep 17, 2014
I'm making an import/export of xml - I have the import of xml sorted I'm just trying to finish off the export. My export class is called XmlWriter.java. Inside the class I have an updateFile method to update an xml file as such:
public void updateFile(Environment environment,Document doc)
{
// code
}
I then in my main method have
public static void main(String argv[]){
//declare new object of class
XmlWriter xmlWriter = new XmlWriter();
//test testUpdate method
// xmlWriter.testUpdate();
Environment environment = ;
[code]....
I don't know what to make my variables equal to - eclipse keeps trying to use null but obviously that won't work. The Environment is another class that just contains getters and setters for the 3 different databases (that are in the xml file) and the getter/setter for the environment ID (also in xml file).
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Jan 10, 2014
How can I make an .exe file for my java project that will work on every computer?
I have a jar file, but the project can not work without installed IntellyJ or other development environment on that computer, i.e. it doesn't work only with installed java runtime.
What can I do to make an .exe file for my java project?
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Sep 29, 2014
I have a jsp with an img tag whose src is set to request a servlet to display a chart. This is called from another jsp form where user can select various filters. The first time the request is made all works great. but if the user changes the filter settings and and makes the servlet request a second time the chart stays the same. I have verified the new filter values are being set but the servlet is only being called on the initial request.at the head or called servlet I have(I also call a jquery empty on the div that holds the chart between requests. at the moment it just displays the former chart). It is like it is using cache:
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
response.setHeader( "Pragma", "no-cache" );
response.setHeader( "Cache-Control", "no-cache" );
response.setDateHeader( "Expires", 0 );
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Mar 9, 2014
I use JTable and JScrollpane in my java application, and I would like for every selected row in the scroll pane, the pie chart to be made for the values in % that the row contain.
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Oct 9, 2014
How would i go about making this NOT resizable?
If I do try to do ChatFrame.setResizable(false); it gives me this error:
Exception in thread "AWT-EventQueue-0" java.lang.Error: Unresolved compilation problem:
Cannot make a static reference to the non-static method setResizable(boolean) from the type Frame
at com.ui.ChatFrame.<init>(ChatFrame.java:37)
at com.ui.ChatFrame$5.run(ChatFrame.java:403)
at java.awt.event.InvocationEvent.dispatch(Unknown Source)
[Code] ....
Here is the code:
package com.ui;
import com.socket.History;
import com.socket.Message;
import com.socket.SocketClient;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
[Code] ....
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Jan 22, 2014
I'm going to make Dekstop Based Home Inventory, do you have a tutorial for it ?
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Mar 10, 2014
I prompted the user to enter inches of rainfall for seven days and stored them in an array. Now, I am trying to display a histogram of this data using a nested loop, but for each inch, I have to display a * like this:
Rainfall Histogram:
****
***
**
******
********
**********
**
The only way I know how to display a number of *s according to user input is by an if statement. I copied and pasted from a similar class assignment I did, so what I have so far is pretty messy and nonsensical:
static char DetermineRainfall(int inches)
{
System.out.println("Histogram");
//char inches;
for(inches = 0; inches < 7; inches++)
{
for(int j = 0; j < 1; j++)
{
if (rainamount > .9 && rainamount <= 1)
inches = '*';
return inches;
}
}
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Nov 28, 2014
I am trying to run a Java applet (.jnlp) file through OSX. The purpose of the applet is to upload files to an SQL server. When I try to run the applet, I get an "Unable to launch the application" error because "No application resources are specified for this platform" After some digging , we noticed there are only resource instructions for "Windows".
Would there be any way possible to make this compatible in an OSX environment through a few alterations to the code, or would this be an issue that the original developers would have to resolve?
Here is the specific code pointing to the Windows Resources:
<resources os="Windows" arch="amd64">
<j2se version='1.6+' initial-heap-size="64m" max-heap-size="512m"/>
<jar href='http://192.168.1.140:7001/MagicInfo/uploader/uploader.jar' main='true' />
<jar href='http://192.168.1.140:7001/MagicInfo/uploader/lib/jnlp.jar' download="eager" />
<jar href='http://192.168.1.140:7001/MagicInfo/uploader/lib/transform.jar' download="eager" />
[Code] ....
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Apr 28, 2015
I am a student in an intro to computer science class working on my final project. This is essentially a game of connect 4, but only requiring 3-in-a-row for victory. We were given the base game and a sample file to work with to make an AI that beats our professor's ai in the base game. Here is the base game
package cs110.project3;
import javafx.application.Application;
import javafx.application.Platform;
import javafx.beans.value.ChangeListener;
import javafx.beans.value.ObservableValue;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
[code].....
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Oct 22, 2014
so for my computer science class, we have the following problem:
In your documentation be sure to say which loop you thought was easier to implement for this program and why Write a program that produces the following outputs. The first line of output must be written using a For-Loop. The second, using a While-Loop and the third using a Do-Loop.
You look at the program and smile because you see that the series is just the numbers 1-10 squared...just one line is in reverse order. No problem! As you start typing you discover that the number 8 key on your keyboard is not working. For this program you are unable to use the multiplication key
So, back to the drawing board. By staring at the sequence a light comes on and you are able to quickly finish this program WITHOUT using mulitiplication (or the Math class/ solve with arithmetic operators +, - or / ) .
Sample output:
For Loop
1 4 9 16 25 36 49 64 81 100
While Loop
100 81 64 49 36 25 16 9 4 1
Do While Loop
1 4 9 16 25 36 49 64 81 100
I have the "for" done, but I did it with a "for" in the beginning but then had a multitude of nested "if" loops so that I could do 7*7=7+7+7+7+7+7+7
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Aug 14, 2014
I want users to input their phone Number But I want to make sure it is a phone number so they don't just do 1 and then leave it.
public static void main(String[] args) {
// Create the Scanner
Scanner in = new Scanner(System.in);
// Create the Variables
int phone;
if(phone > 100000000000 || phone < 100000000000) {
System.err.println("Error");
}
By the Way there are 12 digits in the if statement so that is 11 0's. Because all phone numbers are 12 digits.But when I run it, it comes up with an error saying The literal 100000000000000000000 of type int is out of range.I don't know how to make it so that the int has a limited number.
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Jun 14, 2014
I am having is not being able to print out the diamond the amount of times the user enters (for example, when it asks how many diamonds, I enter a 2 and only one diamond comes out.)
import java.util.Scanner;
public class Pattern5
{
public static void main(String[] args)
{
// For this pattern program, ask the user how many diamonds
// she would like to print to the screen. The following pattern is one diamond.
[code]...
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Mar 7, 2015
I am having a bit of trouble making the '+' add two numbers in java. For example:
When the user enters " + 4 5 " I want it to come out as " 4.00e+00 + 5.00e+00 = 9.00e+00 "
Here is what I have so far:
public static void main(String[] args) {
Scanner in = new Scanner(System.in);
while (in.hasNextDouble()) {
double num1 = in.nextDouble();
double num2 = in.nextDouble();
String s = "";
[Code] .....
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Oct 2, 2014
I need to be able to call this method and it should take the object and, add it to my list of items, but I am having trouble getting it to work. I know the numbers and stuff aren't correct eventually it will add one to the array length when i call add item, but I am just trying to go one step at a time
//creates new MediaItem object and add it to items[]
void addNewItem(String title){
MediaItem object = new MediaItem(title);
MediaItem[] items = new MediaItem[1];
items[0] = ("object.getTitle()");
numberOfItems = numberOfItems + 1;
System.out.println(items[0]);
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