I/O / Streams :: None Of Ports Are Detected - Returns Empty Enumeration
Apr 21, 2011
I've downloaded the Windows version of Java Commnunication API from java.sun.com. I extracted the zip file, placed the comm.jar at c:j2sdk1.4.0jrelibext folder.After that, i wrote a simple program to test whether i can get any serial/parallel port object from CommPortIdentifier.getPortIdentifiers();. It returns an empty enumeration, meaning that none of my ports are detected.
However I have checked that com1 port is exist using hyperterminal. I have RFID card reader and I am trying to read data from rfid card.
I have programmed a Router class which has two methods, receive and send.In receive method it receives the plain text from the server through port 2000.Its now all cool.In send method it sends the message to a client through the port 2001 but at the client i get an exception
connection refused:connect import java.io.*; import java.util.*; import java.net.*; import java.sql.*; class Router { String str; public void receive()
I am trying to create a method called getVariable will has a parameter of a variable that has a type of Test, an enumeration. An int variable called x is assigned a value of 5, and through control statements, I want its value to change depending on what the argument is. I was able to correctly create this method, but when I use it I get an error saying, "non static method getVariable(Test) cannot be referenced from a static context" on line 28.
Here is the code:
package javaapplication5; public class Product implements Cloneable {
I am unable to open Pogo Poker with out receiving an error message saying "Oops, Java is not detected on your computer" (or something similar). I have reinstalled it several times and get the same results.
So I need to write a program that reads through a String and counts how many vowels there are and prints them out as it finds them. This is what I have so far:
While executing my application i came across with this unexpected error which i don't know why?
# # A fatal error has been detected by the Java Runtime Environment: # # EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x000007fdcacd79a9, pid=4980, tid=7724 # # JRE version: Java(TM) SE Runtime Environment (7.0_45-b18) (build 1.7.0_45-b18) # Java VM: Java HotSpot(TM) 64-Bit Server VM (24.45-b08 mixed mode windows-amd64 compressed oops) # Problematic frame: # C [ntdll.dll+0x79a9] # # Failed to write core dump. Minidumps are not enabled by default on client versions of Windows # # If you would like to submit a bug report, please visit: [URL} ..... # The crash happened outside the Java Virtual Machine in native code. # See problematic frame for where to report the bug. #
I've a vertical-bar-delimited file where most elements contain text, some contain whitespace, and some are empty. Examples:
62RG|fe|Pencil Financial Group, LLC||doug@pencil.com|||85637889|Cross, Ben|bcross@godaddy.net|Bernard|Cross|Ben||315 One Tree Hill Terrace|Lafayette|LA
String str_arry = innline.split( "|", 17); lisst.add( new Contact( str_arry));
and my Contact class has the constructor
public Contact( String[] str_arry) { for( int ii = 0 ; ii < str_arry.length ; ii++ ) { if( str_arry[ii].matches("^s+$")) { str_arry[ii] = null; System.out.println("hit a null");
[Code]...
I expect the for-loop in the constructor to find any elements containing whitespace characters and set them to null for subsequent assignment.And when the code runs I do see some hit-statements pop up, so the detecting part is working.
But when I then process the list and access a Contact object and test fields for nulls I don't find any ie
if( aContactObj.getfFCity() == null) System.out.println("city is null");
never prints when it should.
What's the trick? Or is my approach wrong and if so what should it be?
I have a HashMap with multiple values at runtime. In that map one key has empty value , how to avoid this value to add in a list. some code sample is below:
public HashMap getLoop2Map(Map map, String xslFile , int sheetNo){ HashMap hashMap = new HashMap(); try{ ArrayList list = new ArrayList(); System.out.println("-------Map : " +map); list.add(map.values()); //System.out.println("------- boolean : " +val); System.out.println("------List : " +list); }
I do not want to add the empty value in a list ...
result in map
-------Map : {Free Text Entry={}, Mouth / Throat={Free Text Entry={Free Text Entry=<FORMFILENAME>EditChartPhysicalExamText.form </FORMFILENAME><TAG>"<MUSCULOSKELETAL.PE>"</TAG>}, Salivary Glands Condition={Salivary Glands Condition=MouthAttribute}, Examination Overview- Mouth / Throat={Examination Overview- Mouth / Throat=MouthAttribute}, Tonsils={Tonsils=MouthAttribute},
@ManagedBean @SessionScoped public class HelloBean { public void downloadFile() { File file = new File("C:datacontacts.doc"); HttpServletResponse response = (HttpServletResponse)
1) productType that have name and price of the productType and an empty consturcor. 2) superMarket that have name of supermarket and arraylist of productTypes (
private ArrayList<ProductType> products;
) and an empty constructor.
In each class I have function that get input from console and should store it into each class variables.
In productType i have function:
public void getFromUser() throws IOException { BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); System.out.println("Enter product name:"); name = br.readLine(); System.out.println("Enter price:"); price = Integer.parseInt(br.readLine());
[Code] ....
The main is something like:
public static void main(String[] args) throws IOException{ SuperMarket s1 = new SuperMarket(); SuperMarket s2 = new SuperMarket(); s1.getFromUser(); }
The problem is when i get to line "products.add(i,p)" I get java.lang.NullPointerException
In the debug mode I can see that when I get to this line the "products" is null.
why do you think this happening, when I do "new SuperMarker()" in the main it should run the empty constructor and create new arraylist...
I've been beavering away with Java for a few months. But as with all languages the String implementation looks designed to trip up even experienced programmers.
My current development gets data from various sources outside my control. When I get a string I want to test if it is empty/null/or whatever. Simple enough one thinks.
But if you search the internet you see everone seems to have a slightly different approach. So what is the best way of determining that a string is not useful to you?
I've had success with this
if(string == null || string.length() == 0)
But I've seen people using methods - not necessarily of String (e.g equals, empty) and regular expressions.
What is the best approach to this considering coding efficiency and/or processing efficiency (accepting you'd have to be processing a lot of strings for the latter to be an issue).
im trying to make a gui im trying to add a new jbutton for every empty cell in the array, and for some reason its giving me array index out of bounds error, this is what i have, im trying to to do it in an 80 by 80 array.
public JButton[][] buttons = new JButton[80][80];
public void addButtons(){ for(int i=0;i<buttons.length;i++){ for(int j=0;i<buttons[i].length;j++){ buttons[i][j]= new JButton(); } }
I'm writing basically my first program for school. I've written small ones, following instructions, but this is the most vague. I'm having issues. I can't figure out what the error means. I'm not done with the code, but I think the ArrayList is throwing me off. I'm trying to gather user input and sum the total. Here's the code:
package graduationplanner; import java.util.ArrayList; import java.util.Scanner; import java.lang.Double; public class GraduationPlanner { public static void main(String[] args) {
I am learning Java on my own, and I am creating little programs to do so.The program below asks the user to input text and hit enter. When user does that, it asks if that is correct. If the user enters "y," the program ends. That's good.If the users enters "n," the strGrategul is set to empty which triggers the while statement to start over again. That's good. However, when the program asks the user to "Tell me one thing you are grateful for..." it doesn't wait for user input. Instead it skips to "You said ''? Enter 'y' or 'n'" It thinks the user enter an empty line.
I am having issues with the program below everything works but I can't figure out a way to add code that if a user just hits enter without inputting anything it says "entering in nothing is not a valid choice" I am stuck on how to compare a int to a string ...
//import statements import java.util.*; //for scanner class // class beginning public class Guess { public static void main(String[] args ) { //Declare variables area
I am trying to create an array filled with the object Card. It keep throwing the exception that the "deck is empty". I am not sure why that's happening because the code for filling the array seems fine.
public class Deck { private Card[] deck; private CardPile cardPile; private int numCards; public Deck() throws InvalidDataException{ this.deck = new Card[52];
I am trying to create an empty array that has no assigned length as the amount of elements it needs to hold will be dependent on another value. I then want to use a while loop to assign values to it. Here is an example of what im looking for it doesnt work. Iam trying to do:
int x = 12; int i = 1; int k = 0; int[] factors = {} while (i<x) { if (x%i==0) { factors[k] = i; k++; i++;
table.addKeyListener(new KeyListener() { public void keyPressed(KeyEvent e) { if (e.getKeyCode()==KeyEvent.VK_ENTER) { model.addRow(new Object[]{"", "","",""}); } } public void keyReleased(KeyEvent e) { } public void keyTyped(KeyEvent e) { } } );
I've added JTable to JPanel and used DefaultTableModel. I have to add a new empty Row to table after i press enter key. But somehow I've not been successful so far.
It works in the first time. But, after sometime the data is not retrieved and display empty screen. Once, i stop and start the server again, the data is getting retrieved again. But, later when we refresh the empty page is getting displayed again.
