Executing A Program With Several Classes
Apr 29, 2015
I am working my way through "Head First Java" and typing the code in the book into Notepad++ as I go. In the first few chapters the code was simple and only had one class (main). Now the code has two or more classes. Originally I would compile the code in the Command Window by typing "javac" and the program's name. After it compiled I would execute the program by typing "java -classpath . " and the program's name. However, now when program has several classes I get the following error: Could not find or load main class. Below is a program I am having issues with... does it need to be saved as two separate files?
class DogTestDrive {
public static void main (String [] args) {
Dog one = new Dog();
one.size = 70;
Dog two = new Dog();
two.size = 8;
[Code] ....
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Apr 9, 2014
This is a simple project that i was using to test my current java knowledge (kinda like revision) and for that i used two classes to make a simple averaging program. i know i0m making it more difficult but like i said i'm testing myself but i come up with an unexpected error. Here's the code:
- 1st Class
import java.util.Scanner;
public class Main {
public static int num;
public static int total = 0;
public static int average;
[Code].....
Now the problem is after inputing the numbers it doesn't give me the average but the value of 0.
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Aug 15, 2014
The requirements are as follows:Design and implement the class Day that implements the day of the week in a program. The class Day should store the day, such as Sun for Sunday. The program should be able to perform the following operations on an object of type Day:
A. Set the day.
B. Print the day.
C. Return the day.
D. Return the next day.
E. Return the previous day.
F. Calculate and return the day by adding certain days to the current day. For example, if the current day is Monday and we add four days, the day to be returned is Friday. Similarly, if today is Tuesday and we add 13 days, the day to be returned is Monday.
G. Add the appropriate constructors.
H. Write the definitions of the methods to implement the operations for the class Day, as defined in A through G.
I. Write a program to test various operations on the class Day.Should I break down my day.java into several separate classes, one for each of the sections (previous, next, etc)?
import java.util.*;
public class MyDay
{
static Scanner readinput = new Scanner(System.in);
String day;
public MyDay(String day)
{
day = "Sunday";
[code]....
Ideally I would like to create a Gui that would have someone type in the day, and then press a button to return the next day, prior day, or have a text input to test for adding X number of days.
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Nov 29, 2014
At startup, the class containing your main method is loaded. It loads all classes that it needs. Each of those loaded classes loads the classes that it needs, and so on. That can take a long time for a big application, frustrating the user. You can give users of your program the illusion of a faster start with the following trick. Make sure that the class containing the main method does not explicitly refer to other classes. In it, display a splash screen. Then manually force the loading of other classes by calling Class.forName.
I'm not sure if I got this right - the tip amounts to suggesting to load all the classes altogether in the main method while displaying the splash screen?
Second, how can the main method not refer explicitly to other classes? It has to create some objects after all...
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Apr 5, 2015
I am trying to make a program that takes the information from the main args, and displays them as a email in another class when Java is run.
Ex.
From: PersonA
To: PersonB
Email message is here
I have gotten this far, but every time I append my "email.print()" into the next class, it never can print any of the Strings.
Main Args Class:
public class TestMessage {
public static void main(String[] args) {
Message email = new Message("Harry Morgan", "Rudolf Reindeer");
email.append("Dear so and so,");
email.append("It is my great pleasure to");
email.append("write you an email.");
email.append("");
[Code] ....
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Nov 12, 2014
I have a problem with this ascii animation program I am working on. I declared a method inside of my class AsciiAnimation extends JFrame implements ActionListener, called
package AsciiAnimation;
import java.awt.*;
import java.awt.event.*;
import java.util.ArrayList;
import javax.swing.*;
public class AsciiAnimation extends JFrame implements ActionListener{
int currentFrame = 0;
ArrayList<String> frameList = new ArrayList<String>();
[Code] ....
Basically I just am trying to figure out how java works with me accessing those 2 data members, currentFrame and frameList inside of my first class ALL in the same package.
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May 16, 2015
I am not necessarily 'new' to java, however I have always used NetBeans so I am not entirely sure how to do what I need with the terminal commands. I am trying to execute a java jar file(which works perfectly on windows) on the Raspberri Pi, essentially debian linux.
As I mentioned previously, I have a java jar file which I can execute on windows, but it depends on three other libraries, namely RXTX, MySQL, and JSON. I am not positive how to compile this into a jar, or execute it in debian.
This was how I attempted to load two of those libraries, however the last line is the error I received.
Direct copy from the terminal:
pi@raspberrypi ~/Desktop $ java -Djava.library.path=/usr/lib/jni -cp /usr/share/java/RXTXcomm.jar:/usr/share/java/mysql-connector-java-5.1.10.jar:. Automation_System.core.HAS
Error: Could not find or load main class Automation_System.core.HAS
Specifically, the problem seems to be that I cannot use the -cp flag to indicate classpaths, and the -jar flag indicating I am executing a jar in the same command. I am not sure how to point the compiler to my main class HAS in the core package of the jar, and also to the libraries referenced.
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Jul 26, 2014
I'm trying to make a statement of elapsed time print out after I've executed everything with a ThreadPoolExecutor. What happens is that instead of printing out after all the iterations within the for each loop are done, it prints out the elapsed statement in the middle of the iterations or even in the beginning of the whole execute() method. Here is my code:
package com.atem;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadPoolExecutor;
public final class Example {
[Code]...
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Mar 17, 2014
How to correct these warning?
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Dec 14, 2014
I've just installed the last Java kit JDK plus netbeans and I've done my first project in Java. It is running perfect from command line<but is is difficult to execute each time from there my tests> but I couldn't run the jar file from windows with double click he jar file even I've spent 3 hour on google to find different methods (registry modifying, control panel/program running in windows, a patch file etc, ) ....
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Jul 1, 2014
I have been writing some loops for some days now. I'm just unable to predict the output for the following different piece of code even though I wrote 'em
public class Numbers {
public static void main(String[] args) {
int numbers[] = {1, 2, 3, 20, 80, 200};
for(int i = 0; i < numbers.length; i++) {
System.out.println(numbers[i++] = 5);
}
}
}
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Apr 14, 2014
I want to execute a class from src folder in JSP page. But i have receiving the error only..,
Java Code:
<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
pageEncoding="ISO-8859-1"%>
<%@page import="ServerInitiator" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
[Code] ....
My package structure is :
I have try by using the above, is their any perfect way to call this..
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May 27, 2014
I need to execute a perl file from a resource folder, So that i can able to run the perl file after changing the project to a jar file. And also i need to pass an argument also.
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Aug 8, 2014
I am validating an xml file using XQuery in Java using XQJ API. When the query is triggered it is giving the ClassNotFoundException for orai18n.text.OraCollator. I have placed the orai18n-collation.jar file in MANIFEST.MF file and it is loaded in to the class path.
Not sure on why it is giving the exception.
The JDK i am using JDK1.7 and application server is weblogic.
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Mar 21, 2014
When a thread completes its execution, it will be destroyed.In Java thread pool implemenation, how does threads come back to ready state after executing the task.?
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Oct 16, 2014
Find the error log here ......
[pccbuildmgr@svl-jbuild-d1 Logical_Versioning]$ java -jar VersionUpdate1.jar
Picked up _JAVA_OPTIONS: -Xmx10g -XX:MaxPermSize=10g
can get the values for 1.0
java.net.UnknownHostException: home
at java.net.PlainSocketImpl.connect(PlainSocketImpl.j ava:195)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.j ava:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
[Code] ....
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Apr 18, 2014
How do you call classes within other classes? Or can you only call classes through the main?
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Feb 14, 2015
I'm doing an aggregation exercise that's suppose to find the volume and surface area of a cylinder. What I'm trying to do is pass values from one class, to a second class, and that second class passes values to a third class.
This may be a clearer explanation: The first class is the main program which sends values to the second and third class. The second class is used do calculations for a circle (a pre-existing class from another assignment). The third class grabs the values that the second class calculated and calculates those values with the one that was passed from the first class to the third class. The first class then prints the outcome.
Problem is when the program gets to the third class, it just calculates the value from the first class with the default constructor from the second class. It's like the second class never received the values from the first class. I think I'm missing a step, but I don't what it is.
First Class:
package circle;
import java.util.Scanner;
public class CylinderInput
{
static Scanner in = new Scanner(System.in);
public static void main(String[] args)
{
//user defined variable
[Code]...
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Dec 26, 2014
Why do we get such output or which line of code produces the output?
1class Egg2 {
2 protected class Yolk {
3 public Yolk() { print("Egg2.Yolk()"); }
4 public void f() { print("Egg2.Yolk.f()");}
5 }
6 private Yolk y = new Yolk();
[Code] ....
/* Output:
1.)Egg2.Yolk()
2.)New Egg2()
3.)Egg2.Yolk()
4.)BigEgg2.Yolk()
5.)BigEgg2.Yolk.f()
*///:~
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Oct 18, 2014
I'm quite new to Java. I have some trouble with understanding how to get two classes to get objects from each other (if that is the correct term).
Lets say I have a login class, in which I have a method checking what the user has entered into the console (I have not displayed the whole code, but this class works as it should and give the user an option to enter username and password and return it true if entered correct).
public static boolean validateUserPass(String userName, String password) {
String[] user = {"admin"};
String[] passwords = {"firkanten"};
boolean check = false;
for (int i = 0; i < user.length; i++) {
if (userName.equals(user[i])) {
if (password.equals(passwords[i])) {
check = true;
Now, in another class I want a display box to appear on the screen and give the user three options: Click yes, no or cancel. I get this to run perfectly alone, this is not the hard part for me. I want the display box only to appear when the correct username and password is given, but I can't seem to figure out how to do this probably.
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Feb 7, 2014
Regarding the code examples in Head First Java, this is from Chapter 5, regarding the beginning creation of the dot com game. There are two classes in quesiton
the first is the SimpleDotComTester class:
public class SimpleDotComTester {
public static void main(String[] args)
{
SimpleDotCom dot = new SimpleDotCom();
int[] locations = {2, 3, 4};
dot.setLocationCells(locations);
String userGuess = "2";
String result = dot.checkYourself(userGuess);
}
}
and the second one is the code for the checkYourself () method in the SimpleDotCom class
public class SimpleDotCom {
int[] locationCells;
int numOfHits = 0;
public void setLocationCells(int[] locs)
[code]....
Now I noticed that both classes use a variable called result; the program runs fine, but assume from the example that you can use the same variable name two different classes;
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Mar 29, 2014
design a class to conduct a survey of three hospitals. you want to know how many sectors (eg operation, children, gastronomic) each hospitals have, and how many doctors there are in each sector.
what is the process of class design?
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Jan 5, 2014
I have a Date class and Time class. Is it possible to pass Time object inside Date constructor so that toString function gives output as 12/05/2013 06:31:30 ?
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Apr 24, 2014
I have two classes.
First and Second.
In First class I want to use methods from Second class. So:
Java Code:
Second s = new Second();
s.secondMethod(); mh_sh_highlight_all('java');
Second thing I want to do is use JTextArea from First class in Second class.
So since it gives me error, I extended First class with Second:
Java Code: public class Second extends First { mh_sh_highlight_all('java');
It look like it should work, no errors etc. Also both things are working separately. But since I used both at once...
Java Code:
Exception in thread "AWT-EventQueue-0" java.lang.StackOverflowError
at package.Second.<init>(Second.java:7)
at package.First.<init>(First.java:17) mh_sh_highlight_all('java');
I can move what I need to First class, and it will work fine, but I want to make this in two classes. But I really don't understand extends, I just use them if there is need for them. So I don't know how to handle this problem.
I also tried to extends Second just like First:
Java Code: public class Second extends JPanel implements ActionListener { mh_sh_highlight_all('java');
Instead of extending First, but it can not be done, since ActionListener is in First...
Well. Also addActionListener can maybe solve my problem?
I'm using:
Java Code: xx.addActionListener(this); mh_sh_highlight_all('java');
Maybe I can use something instead of this? But what?
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Jan 19, 2015
Wondering, what is exactly reason for existence of inner classes? Are there problems that without them you can not resolve?
Anything beside emulate multiple inheritance - when your class need to extends the real classes, and not implement multiple interfaces ?
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Mar 28, 2015
I have a folder of classes that I am packaging together. Some classes are being packaged and compiling just fine. My other classes in the same package, however, are saying that they cannot find these classes.
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