How To Organize Queries In Java Source Code
Oct 7, 2014
Lately I've been working with JDBC and writing queries in some Java programs. I've noticed that I keep experimenting with where I place my blocks of querying code. I've tried creating a private method in the class where the query is used, I've created utility classes where I can call the query when needed, and sometimes I've just put it in a localized block of code where I need to. Also, most often these queries are one-shot queries where I need to pull the data to populate a JTable.
In short, this has made me realize that I don't have a solid practice for organizing my queries in Java. So my question is "Is there a practice for organizing query code?".
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Feb 16, 2015
When I run this (entering 12 for both questions) I get this error:
java.lang.ArrayIndexOutOfBoundsException: 12
at MathTablesTwo.main(MathTablesTwo.java:22)
Also, what would be the proper way to organize my code into blocks?
import java.util.Scanner;
public class MathTablesTwo {
public static void main(String args[]) {
Scanner input = new Scanner(System.in);
[code]....
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Feb 19, 2014
I have been given a task to scan the contents of a websites source code, and use delimiters to extract all hyperlinks from the site and display them. We havent been told anything about how to do this so after some looking around online this is what I have so far:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Scanner;
[Code] ....
So my program can extract each line from the source code of a website and display it, but realistically I want it to extract each WORD as such from the source code rather than every line. I've looked around online but I don't really know how it's done because I keep getting errors when I use input.read();
How to make it extract each word from the source code?
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Feb 3, 2014
Why is this not valid in java:
Both uses public with the same class/interface name.
Test.java:
public class Test implements Test{
/// Some codes
}
public interface Test {
///Some methods
}
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Feb 21, 2015
How to deploy Java Swing application as windows software. I have tried the following to do this :
I have created jar file for my project after that created exe file using Launch4j and Advanced installer, exe file produced by both software are working fine but those are placing the jar file inside that exe file, My problem is any one who has that exe file can extract and view the source code by decompiling java class file. Is there any way to deploy java application without decompiling the code.
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Oct 31, 2014
I am trying to complete this question. I understand the most of it but I haven't go a clue to read in the file name.
Full question: Implement a program that reads in a Java source code file and checks to see if it has balanced {}brackets. Your program should use a stack, implemented as a linked list, to check the brackets.
NOTE: you can use a reference called top which points to the head of the list. Your program should run as a command line program and should take a filename as an argument and print one of BALANCED or NOT BALANCED.
For example: c:> java checkBalanced "myProgram.java" BALANCED
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Jul 11, 2014
1.Is there any way by which i can see what is happening inside pre defined methods.
i.e. can i see there source code?
2.Somewhere i learned how to see the content of a pre defined class i.e. by using:
javap java.io.classname
but i dont know what javap means!
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Mar 30, 2014
To be specific, how can I use enumeration of one source-code file in another.
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Apr 13, 2014
I am trying to write a program that read from a csv file called matches.csv.
A single football match can end with a win or a draw: in first case the winner team get 3 points and the loser none, in the second case of draw each of the two teams get 1 point.
For example, the first line of the file matches.txt is as follow:
In the file it contains the following data.
17/08/2013ArsenalAston Villa13
24/08/2013Aston VillaLiverpool01
This means that a match has been played on the 17/08/2013 where Arsenal scored 1 goal while Aston Villa 3 goals: thus Arsenal got 0 points while Aston Villa 3 points.
How can I structure my output to make it make it read
Position Team Played Points
1 Aston Villa 2 3
2 Liverpool 1 3
3 Arsenal 1 0
import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;
public class Teams {
public static void main(String[] args) {
String fileName = "matches.csv";
File file = new File(fileName);
[code]....
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Oct 9, 2014
"If you define a public class or an interface in your class, then it should match the name of the java source code file."
Does the statement above mean the following should compile fine ?
public class Animal{
public class Animal{ }
}
The author gives an example saying that if you have a class Multiple.java and in that class, you have:
public class Multiple{}, then it should compile.
But this does not compile. I tried it.
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Oct 19, 2014
I'm doing homework and as far as input, my assignment reads: "Your program must take as input the name of a Java source code file such as the source file containing the source code of this assignment." So my question is, how do i do that without linking the directory directly (i.e. C:/users/...)? I'm using FileReader as shown below...
public static void main(String[] args) throws Exception {
FileReader file = new FileReader (WHAT GOES HERE???);
BufferedReader reader = new BufferedReader(file);
String s = "";
String line = reader.readLine();
[Code] .....
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Apr 8, 2015
I want to extract a specific String from HTML, specifically, I want to extract a String from in between <...>
So far, I've got this
package main;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.URL;
import java.net.URLConnection;
public class HTMLGrabber {
static String allOneString = "";
[code]....
The problem I have is when I change the last parameter in this line:
System.out.println("And the Keywords are:
" +allOneString.substring(allOneString.lastIndexOf("meta name="keywords" content=") + 30, allOneString.indexOf("Fictional History">")+17));
to
System.out.println("And the Keywords are:
" +allOneString.substring(allOneString.lastIndexOf("meta name="keywords" content=") + 30, allOneString.indexOf("">")));
i.e. the generic alternative, I get this error message:
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -366
at java.lang.String.substring(Unknown Source)
at main.HTMLGrabber.main(HTMLGrabber.java:45)
Is there a better and simple way to extract a substring?
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Sep 5, 2014
I am developing an inhouse project in my organization. I unable to implement the pdf uploading, downloading, report generation logic as i am totally new to this implementation.
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Feb 5, 2013
javax.xml.parsers.DocumentBuilder can build a document from a single stream which is the XML file. However, I can't find any way to also give it a schema file.
Is there a way to do this so that my XPath queries can perform type aware queries and return typed data?
We presently use dom4j/jaxen and it does this fine but I figure we should switch to the standard Java runtime if this has been added.
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Apr 29, 2015
I am operating java from the command line (using Terminal on Mac OSX 10.9.5).The current directory within Terminal is called "orange" and the following sourcecode file is in the orange directory :
Test1.java
package orange;
public class Test1 {
public static void main(String[] args) {
System.out.println("Test1 works");
}
}
This complies to Test1.class (visible in the orange directory) but when I try to run it in Terminal (simply using "java Test1" from within the orange directory). I get the following error message (which I don't get if I simply comment out the line //package orange;)
Exception in thread "main" java.lang.NoClassDefFoundError: Test1 (wrong name: orange/Test1)
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:800)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
at java.net.URLClassLoader.defineClass(URLClassLoader.java:449)
[code]...
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Mar 23, 2014
I am building a room management system in Java (Netbeans) and Ms Access. The jasper report is only showing code (source view) instead of design view. The GUI JFrame and Login JFrame are not displaying records in the database and the buttons are not working. Also the labels and text fields are not neatly arranged. The connection to the database is not displaying records.
Connection to the database. COIRMS.java
package Login;
import java.sql.*;
public class COIRMS {
Connection con;
Statement st;
ResultSet rs;
public COIRMS ()
[Code] ....
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Apr 10, 2014
my course material is due for term 1 of my cert 4 programming course, but My lecture will not pass my java projects because there is no source files generated for them in the net beans project structure, tried building, cleaning and building, all i can think of?, tried IDE's 7.4 and 8.0 .
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Sep 9, 2014
I want to trace how many wifi signals are available near some source within some distance in JAVA. How do I do that?
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Feb 14, 2014
I am looking for a way to compile Java Source-Files at runtime and save them all in an executable jar; almost like an IDE would do. I know that there is the javax.tools package which provides a JavaCompiler interface and you can use ToolProvider.getSystemJavaCompiler() to get an instance of a compiler. However, this method has one important problem: it only works on machines that have the JDK installed. Not when only the JRE is installed.
I guess at this point that I need some kind of third party library that offers an implementation of a JavaCompiler. Unfortunately, this is really complicated to search for on the internet since all top listings when searching "compile java at runtime jre" do not really provide a solution to the problem.
I am writing a (somewhat) complex simulation software right now which is supposed to be used by people who have absolutely no knowledge of programming. At the same time, this software should provide the user with a certain amount of flexibility and control over the flow of the simulation.
My previous take on this problem was to build a complex system to interprete user settings from a GUI. I would basically read the GUI input, output it to some kind of own scripting syntax which I just quickly made up and have that interpreted at runtime. Then I realized, that is a silly concept and I threw it out before I got far into the developement.
The much better solution I came up with is taking the input from the GUI, create java source code from it and compile it at run-time. Seems much cleaner and nicer to me; will also probably have a better performance, but thats not really an issue anyways.
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Oct 8, 2014
If I wanted to take strings in from the user through a GUI say day, month, year. I am looking for a way to organize those incoming strings. I am going to add this information to a queue. However, I want the people who put in the earliest day, month, and year to be put into the queue first followed by the next earliest so on and so forth.I was thinking what I would need to make a method that would compare the information.
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Feb 10, 2015
how java imports libraries from a jar file inside a source. Let's say I have the following code on Something.java file,
import com.mycomanyA.*;
import com.mycomanyB.*;
public class Something{
public static void main(String ... args){
// code goes here...
}
}
And the Something.java is inside the following structure...
A.jar
com/
mycompanyA/
A.class
Another.class
B.jar
com/
mycompanyB/
B.class
neededImage.gif
bin-folder/
org/
apache/
Something.java
To compile this code(Something.java) from command line I want to use the following command,
javac org/apache/Something.class
And for the compilation to be successful, I'll have to be just above bin-folder because...
- > Only then my default class path will be (.) and java would automatically include A.jar and B.jar(the other way is to add the jar files using -cp argument, which I want to avoid in this scenario)
- > And for the import org.mycompanyX to work I'll have to be in the (.) directory.
Are my assumptions correct about how java find jar contents imported in a source file?
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May 28, 2014
I am looking for pure java API to be able to create/read outlook tasks.
Any open source API's available for the same.
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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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Apr 13, 2014
I'm trying to program a tile-based map editor and most of it is going quite smoothly except trying to organize the layout. Originally I was going to use 2 frames, one for the map, and 1 for the tile set, but after reading about frames I learned that that is bad practice and is also inconvenient because there is no way to have both frames in focus at once (so you need to click an extra time to gain focus when switching windows). So what I'd like to do is create a single frame application that holds 3 panels. One for the map, one for the tile set, and one for tile settings. This is basically what it would look like:
Note that the tile settings panel uses GUI elements (a border, a JLabel (which starts out empty), a JComboBox, and a JTextField) while the other 2 panels are just drawing panels*
Now I have tried multiple things which either did not work visually (panels were inside panels) or did not compile. One thing I tried was using BoxLayout to put the 2 tile panels vertically within a temporary panel which I then tried to add into the frame after the map panel (with FlowLayout), but that made it look like this: I honestly don't know what else I did that I should write here because in retrospect many of the tings I tried were silly or I don't remember exactly what I did. What would be the best layout to doing what I want?
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Jun 6, 2010
This is my code-
<%@ page contentType="text/html; charset=iso-8859-1" language="java" import="java.sql.*" errorPage="" %>
<body>
<center>
<form>
<table border="0">
<tr> <td> bulbtype </td>
<td> <input type="text" name="bulbtype"></td> </tr>
[Code] ....
Im getting this error:
An error occurred at line: 24 in the jsp file: /bulb1.jsp
bulbwatts cannot be resolved
21: Statement stmt=conn.createStatement();
22: Statement st=conn.createStatement();
23: ResultSet rs1 = stmt.executeQuery("select * from bulb where type="+bulbtype);
24: ResultSet rs2 = st.executeQuery("select * from bulb where watts="+bulbwatts);
25: %>
26: <%while(rs1.next()){%>
27: <tr> <td>name1</td>
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Mar 20, 2014
I'm currently taking a computer program design class which has done a lot for my understanding of how to organize classes, but isn't giving me challenging enough assignments and I don't believe it's going to be covering interfaces and abstract classes, which is a shame. So I've been digging into these topics myself and decided to work on my own program (an Uno game program) that would utilize everything we've been learning and give me some practice with GUIs.
My current plan:
Have an abstract UnoCard class that determines the basic properties/methods common to all cards. Create a class for each card type extending from UnoCard, which would be - the generic card (number and color), action cards (skip, reverse, draw two), and special cards (wild, wild draw four, and blank).
Two enums, one for color, one for rank (which includes the numbers, as well as the action and special card ranks (reverse, wild, exc.) ).
A deck class would have an ArrayList <UnoCard> property and it's constructor would initialize a fresh deck.
A hand class that also has an ArrayList <UnoCards> where it gets said cards from the deck class.
A discard pile class, which contains the cards discarded and the current card in play.
A "board" class (haven't figured out a better name for it yet) which would determine/keep track of the number of players/hands, the turn order, the locations of the cards, and the winning condition.
Area of confusion and concern I'm having:
From what I've read, I want to avoid circular dependency. So if that's the case, when a card type effects the state of a "hand" or the turn order or really anything else, then in what class do I place the method(s) that effect that? If I place it in the specific card class, wouldn't that create a circular dependency? So would it be better then to have the hand class figure out what can be done with a specific card and what that specific card effects (which wouldn't that hinder the cohesion of the class?)?
I was also thinking a possible solution might be to have the non-generic card types contain methods that return values as apposed to manipulating higher level classes, such as a boolean drawCards which returns true if cards need to be drawn, false otherwise (same for skip, reverse, exc.).Then maybe the board class can determine what to do if those values are true or false (which actually seems more convoluted since only one value would be allowed to be true at any given time).
The other solution I was considering is to have a single UnoCardRules class, which serves the sole function of providing methods to determine the effects of each card, that way each card class can only worry about defining the card's state.
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