File Creation - Deletion With Do While Loop
Mar 9, 2015
I have just started to learn Java and have come across a small bump in the road, In the book I am reading it shows an example program using java.io.File with the line File javaFile = new File("test.txt");
The program then goes on to ask if you would like to delete the file with a small do while loop.
Anyway, try as hard as I can I cannot located the test.txt file on my system! is there a reason for this? The program runs fine and has no errors and if I manually create the txt file it will delete it, but it doesn't seem to create the file in the first place.
Why the file is not being created?
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Mar 26, 2015
I know I'm missing something simple, but not sure what. When running the following I have to enter the name of the output file twice.
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
public class IODemo {
[Code] ....
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Apr 3, 2014
I am making a Java project using Eclipse,oracle 10g and Apache tomcat.
Now my problem is that I cant create a session for the users. I have coded on jsp pages mostly.
Session creation using HttpSession through servlets or jsp
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Aug 8, 2014
I am trying to create a Android game. The game is a card game, where each card has a different action and has a different effect. My first thought was to create a Card class and somehow dynamically change the action method for each instance. However after a little bit of research it seems that may be too difficult. A different idea is that I create a class for each different card, and therefore can define the action method different for each one. However currently there is at least 300 cards and therefore I would need 300 different classes, which seems excessive.
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Feb 7, 2015
I'm making a code for a log in system that allow me to verify if username and psw are correct (using a file txt as refer), and then i will add maybe the possibility to sign up.
The fact is that I want this kind of formatting on the .txt
username psw
username psw
username psw
...etc
So I have to read the lines and split to the " " and compare the insert data and the read data.
Here is my code, it star but give me this error when i insert any word
XML Code:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 1
at prova.main(prova.java:20) mh_sh_highlight_all('xml'); Java Code: import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class prova {
public static void main(String[] args) throws FileNotFoundException {
[Code] .....
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Jan 26, 2015
I am creating a simple tiled minecraft like game in java, but i dont know how to make the game loop.Here is the source:
package net.pltformgame.main;
import java.awt.Color;
import java.awt.Graphics;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import javax.swing.JFrame;
public class main extends JFrame implements KeyListener {
[code]...
I really dont know how i make the jump or the game loop.
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Mar 25, 2014
How could we create excel sheets(xls) in java?
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Oct 25, 2014
So, I've been working on creating a text-based game engine that would create games similar to Achaea. It's been working pretty well so far. I just finished creating a great mapping system, but now I've run into a problem. I have a mapping system, but actually creating a map would prove to be quite a lot of work. Each location that the player can be inside of has a name, description, map symbol, and an array of the things inside of it. How can I make some sort of map creation program or something so that I can create my maps more easily?
I thought perhaps making a constructor that accepts a list of files, the first containing a table of strings for the names, the second containing a table of strings for the descriptions, etc.; but it seems that would be quite tedious and may be more complex than actually just hard-programming maps.
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Mar 3, 2015
Now, I would like to properly stop the server. For that, I can do server.stop(); . However, this does not work since the object server is not public, it is contained within the public pc_proxy class.How do I do that?
Java Code: import java.net.*;
import java.io.*;
import com.sun.net.httpserver.*;
import java.util.concurrent.Executors;
import java.lang.reflect.Array;
[code]....
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Aug 15, 2014
I have a couple of objects, which I will call height and width. The latter may depend on the former and I access them through an interface:
interface Height
{
double getHeight();
}
interface Width
{
double getWidth( Height height );
}
I then have something I will call a RectangleMaker, which represents some set of rectangles that can be made. It takes a list of heights and widths and keeps track of which ones have been selected and which ones can still be made. For example, the possible heights might be 2 or 3 and the possible widths 3 or 4. It needs to determine if it can make a rectangle with a specific area and if selected to make that rectangle, disallow any other heights. So if I said, you are in charge of 2 x 3 rectangles, it could still potentially also make 2 x 4 rectangles, but 3 x 3 rectangles would no longer be an option. For the most part I think these details are irrelevant to my question, which is really about organization and assignment of responsibilities.
interface RectangleMaker
{
void setHeights( ArrayList<Height> );
void setWidths( ArrayList<Width> );
boolean isAreaAvailable( double Area );
void selectDimension( Height height, Width width );
Height listAllowedHeight();
ArrayList<Width> listAllowedWidths();
}
Now I have a new requirement. The lists of heights now need to be associated with a source, as do the widths. I should keep track of a list of RectangleMakers and pick the 'most appropriate' one for a particular area. The rule is to sort first on the height source and then on the width source and the first one able to handle the area, gets the job. So I created two enums heightSource and widthSource and had RectangleMaker implement Comparable, so I can make an ArrayList<RectangleMaker> and sort it based on the rules. Then I traverse the list and the first one that returns isAreaAvailable() true gets the job.
The final bit is that these sources also imply a specific set of Heights or Widths. How I get that set varies, it may be a fixed value or values, or might be read from a file. So in principle I could have:
ArrayList<Height> buildHeights( RectangleMaker.SOURCE source )
{
switch ( source )
{
}
}
and have a lot of specific code that builds each list by whatever method is appropriate. I still need to deal with the fact I might need additional information to build the lists. For example, one source might require a min, max and increment and another might require a file name. So I started working in the direction of more interfaces.
interface HeightList
{
ArrayList<Height> getHeights();
RectangleMaker.Source getSource();
}
I am not totally comfortable with my enum lists. They solve the sorting problem, but I am not exactly sure which class should define them. Right now they are defined by the RectangleMaker. I would need to update this class every time I added an implementation of HeightList or WidthList.
I was also thinking that since the list is built from a specific source, that source should be associated with the list. That would lead me to make this change:
interface RectangleMaker
{
void setHeights( HeightList heightList );
void setWidths( WidthList widthList );
boolean isAreaAvailable( double Area );
void selectDimension( Height height, Width width );
Height listAllowedHeight();
ArrayList<Width> listAllowedWidths();
}
It seems maybe there should be a factory in here somewhere, but this is where I am having trouble sorting out exactly who has what responsibility. I can do this sort of thing with my HeightList interface:
class SpacedHeight implements HeightList
{
int start;
int end;
int step;
ArrayList<Height> heights;
RectangleMaker.SOURCE source;
[Code] ....
Should I be thinking of putting one more layer over all of this? What complicates my thinking are two things: multiple instances may have the same source and some of these instances are dynamic. For example, two SpacedHeight instances may have different ranges, but they are both SpacedHeight and it doesn't matter which gets picked first. Exactly what SpacedHeight instances get created is determined by prompting the user for the values. If the heights come from a file, every instance would be associated with a different source and the file names would be hard-coded.
I think I want to make a HeightFactory and I think then it would make sense to move my enum definitions there. I see how I would do that if I could hard-code a specific instance of a HeightList with a specific enum. I am less clear on how to handle the case where the factory needs different parameters for different HeightList implementations.
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Jan 21, 2015
I am working on a UI in JavaFX and create several instances of a custom control class. The control consists of a Pane which wraps several other containers, one of which contains a Circle shape.
At one point, I instance this control and access the Circle shape directly. I transform it's center coordinates (which are always {0.0, 0.0} ) to Scene coordinates. The problem is, the transformation always yields coordinates that correspond to the upper left corner of the control's root pane.
In other words, it's as if the Circle is positioned at the upper left corner of the custom control (when, in fact, it's positioned near the lower right corner).
I have other instanced controls already in the scene, and they do not have this issue - converting the Circle's coordinates to scene coordinates works as it should.
It seems obvious that I'm accessing the Circle too soon - that perhaps the scene graph hasn't been fully traversed for the control and the Circle's position within the control's hierarchy hasn't been updated. I've verified that my attempt to access the Circle's center coordinates occurs after the control's initialize() method is executed, so how to ensure the control's scene graph has been fully updated before I try to manipulate the control...
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Oct 27, 2014
I'm trying to write a transparent proxy like polipo. Polipo is written in C and I want to have the same result in java.
A simple program that can filter/monitor all connections created and closed by the browser.
To do so, I've chosen to work with sockets, because that's the only way i know to read and write raw data to and from the browser in a completely transparent way.
In this moment my code reads and writes every couple of request/response but I've noticed profiling it that the time needed to create the socket is a bottleneck.
Using URLConnection to create the same connection I need much less time than sockets.
When socket creation implies 50ms URLConnection implies only 1ms.
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Mar 21, 2015
I have my code in 3 different files using encapsulation (Data hiding) and i have 1 problem at the very end of my code in my if and else statement (very bottom) when trying to call the classes from the other 2 documents. I will put the code in 1st document to 3rd document.
// FIRST DOCUMENT
public class CollegeCourse { //class name
//variables
String deptName;
int courseNum;
int credits = 3;
double fee;
[Code] ....
UPDATE: error message is
UseCourse.java:24: error: cannot find symbol
LabCourse lc = new LabCourse(department, course, Credits);
^
symbol: variable department
location: class UseCourse
UseCourse.java:24: error: cannot find symbol
LabCourse lc = new LabCourse(department, course, Credits);
[Code] ....
4 errors
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Jul 13, 2014
I am trying to read from a file and storing them back in the file but its not working, I think the way I am reading is wrong or something. Is the for loop correct way ?
try {
in = new BufferedReader(new FileReader("Events_data.txt"));
for (int x = 0; x <= Events.length; x++) {
tid = in.read();
te = in.readLine();
[Code] .....
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Oct 22, 2014
I have to read from a file that is formatted like that :
name
status
friend
END
name
status
friend
END
.. etc
could be more than one line of friends, which where I have my problem. I can't get it to check if after the friend name the word "END"
I have tried to write a while loop inside the main while loop but it didn't work, and now I have tried to check that in a separate function which it also failed, thats my two while loops
BufferedReader br = null;
FileReader fr = null;
int getLine = 0;
try {
String line;
fr = new FileReader(fileName);
br = new BufferedReader(fr);
[Code] .....
Most of the time I got nullPointerException or missed up order for printing the file !!
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Oct 6, 2014
I am trying to read from a text file that has that contains a list of stock tickers and pairs letting the user choose a ticker and provide analysis of stock. Given a ticker from the user provide
1) the max price, the min price and the avg price of the stock from all lines in the file.
2)Additionally the user should be able to find the stock with the highes price as well as the lowest price in the list.
3)lastly the user should be able to specify a different filename for the stock file.
Im trying to do part 1 and I am having trouble trying to read the whole text file and outputting the stock price with the max,min and avg. Am I heading towards the right track at least? Keep in mind I have just attempted trying to read the text file I have and not tried to find the max or min or avg Right now my code is crashing when I enter the stock ticker that is my primary concern.
package hw01b;
import java.util.Scanner;
import java.io.*;
public class Hw01b
{
static Scanner in = new Scanner(System.in);
static Scanner console = new Scanner(System.in);
[Code] .....
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Dec 2, 2014
I have the following unit test that gives me a null pointer exception. The debugger goes to the finally block right after the line that creates a connection factory. Here's the test:
@Test
public void receiveMessage() throws Exception {
MessageConsumer consumer = null;
ConnectionFactory connectionFactory = null;
Connection connection = null;
Session session = null;
Destination destination = null;
[code]....
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Mar 14, 2014
The problem i believe is that I have the max value set to the first value given out, but every time the loop repeats the Max value gets reset to the next value in the file.
Essentially the program is supposed to read a list of credit card transactions and tell the user which transaction is the highest.
Here's the list of the sample file, note that the number of transactions could change that's why i haven't tried simply passing the values to method.
Bicycle 562.90
Groceries 138.43
Hotel 612.00
import java.io.File;
import java.io.IOException;
import java.util.Scanner;
public class CreditCards {
public static void main(String[] args) throws IOException {
String fileName = "C:/Users/David/Desktop/CreditCard.txt";
File inputFile = new File(fileName);
[Code] ....
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May 6, 2015
I'm supposed to add characters to a stack and pop them once the adjacent delimiter is read in from a text file. Moreover, program is supposed to print out the incoming text from the file, but stop when the applicable delimiter is not on top of the stack. As in, a '[' doesn't have a ']'.
I've got the program so it can pop and add to the stack correctly, and stops adding at the correct time, but I cant seem to get it to stop printing. I know a switch statement method in another class seems obvious, but I was trying to practice nested loops.
This is the main program:
import java.io.*;
import java.util.Scanner;
import java.io.IOException;
import java.util.Stack;
public class DelimiterChecker {
public static void main(String [] args) throws IOException {
[Code] ......
Moreover, the file I'm reading for is simply:
{
System.out.println(1)
System.out.println(2)
System.out.println(6 <-------------missing delimiter
System.out.println(7)
}
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Nov 7, 2014
How can I write a method that takes a string with duplicates letters and returns the same string which does not contain duplicates. For example, if you pass it radar, it will return rad. Also i would like to know how can I Write a method that takes as parameters the secret word and the good guesses and returns a string that is the secretword but has dashes in the places where the player has not yet guessed that letter. For example, if the secret word is radar and the player has already guessed the good guesses letters r and d, the method will return r-d-r.
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Oct 10, 2014
So I have this stack. I'm writing out all the operations and what not but I'm having trouble bypassing this "generic array creation" problem. I'm meant to be creating an array based implementation of a stack and from my research from google and my various attempts at things, I have not found a solution that works.
In addition; I have all the operations written that I need except for one final one. And that is clear(). clear() is meant to empty the array, essentially it is a popAll() method. Then all I need to do is set up so I can print out the arrays and I should be able to handle everything else.
StackInterface:
/**
An interface for the ADT stack.
*/
public interface StackInterface<T>
{
/** Adds a new entry to the top of this stack.
@param newEntry an object to be added to the stack */
public void push(T newEntry);
/** Removes and returns this stackÕs top entry.
@return either the object at the top of the stack or, if the stack is empty before the operation, null
*/
public T pop();
[Code] ....
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Jan 27, 2015
I am trying to print a loop inside an array of a greater size than the loop itself. Like for example I have an array of size 7 but it has only 3 elements.
int[] array=new int[7]
array[0]=2;
array[1]=3;
array[2]=4;
now what I want to do is print these three numbers in a loop so that my array[3]=2;array[4]=3;array[5]=4 ...... till the last one. Also the array could be any size and not just 7.
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Feb 25, 2014
Here's the code: it's while loop inside a for loop to determine the proper length of a variable:
for (int i = 0; i < num; i++) {
horse[i]=new thoroughbred();
boolean propernamelength = false;
while (propernamelength==false){
String name = entry.getUserInput("Enter the name of horse "
[code]....
I was just wondering what was going on here -- I've initialized the variable, so why do I get this message? (actually the carat was under the variable name inside the parentheses.
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Nov 2, 2014
I have everything else working. My problem is that when i type "quit" to close the outer loop. It still runs the inner loop. The National Bank manager wants you to code a program that reads each clients charges to their Credit Card account and outputs the average charge per client and the overall average for the total number of clients in the Bank.
Hint: The OUTER LOOP in your program should allow the user the name of the client and end the program when the name entered is QUIT.In addition to the outer loop, you need AN INNER LOOP that will allow the user to input the clients charge to his/her account by entering one charge at a time and end inputting the charges whenever she/he enters -1 for a value. This INNER LOOP will performed the Add for all the charges entered for a client and count the number of charges entered.
After INNER LOOP ends, the program calculates an average for this student. The average is calculated by dividing the Total into the number of charges entered. The program prints the average charge for that client, adds the Total to a GrandTotal, assigns zero to the Total and counter variables before it loops back to get the grade for another client.Use DecimalFormat or NumberFormat to format the numeric output to dollar amounts.
The output of the program should something like this:
John Smith average $850.00
Maria Gonzalez average $90.67
Terry Lucas average $959.00
Mickey Mouse course average $6,050.89
National Bank client average $1,987.67
Code:
public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
String name = "";
int charge = 0;
int count = -1;
int total = 1;
int grandtotal = 0;
int average = 0;
[code]....
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Mar 8, 2014
How to convert this program from a while loop to a for loop.
import java.util.Scanner;
public class LongDivision {
public static void main(String arguments[]){
Scanner input = new Scanner(System.in);
System.out.println("Enter the dividend: ");
[Code] ....
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Feb 17, 2014
How do I convert my for loop below to a while and do while loop?
for(int a=1;a<=9;a++){
for(int b=1;b<=a;b++){
System.out.print(a);
}
System.out.println();
[Code] .....
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