Variables Over Methods - Unresolved Compilation
Mar 17, 2015
I'm making a java program that can "convert" java to arduino by sending commands over a serial port. I'm using the JSSC library, and using methods to shorten things up a bit.
I've already made the code that starts up the serial port and it does connect. But I've made two different classes for the methods. One for the RXTX and one for the Arduino.
I'm making it so that I can just type:
Java Code:
public static void main(String[] args) {
RXTX.SerialSetup();
Arduino.pinMode(2, 0);
} mh_sh_highlight_all('java');
And it will start the serial port and set pinmode on pin 2 to output.
But when I try it I get this error:
Java Code:
Exception in thread "main" java.lang.Error: Unresolved compilation problems:
serialPort cannot be resolved mh_sh_highlight_all('java');
I don't know if its possible to 'send' a variable to a different method.
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Oct 24, 2014
I have the following 2 classes:
class Address {
private int a;
public void set_a(int a) {
this.a = a;
}
}
class Person {
private Address address;
}
How do i access the method set_a() (through the "address" in Person) from another class which contains main() ?
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Jan 8, 2014
Do inherited methods use their instance variables or do they use the ones in the method that inherits them?
For example, Class B extends Class A. Class A and B both have the instance variable "potato". A client program tries to use method "cut" using an object of Class B, but class B has no cut method. So, class B uses the "cut" method inherited from class A. What I want to know is will that cut class A's potato or class B's?
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Feb 24, 2012
i'm trying to modify and use a GUI to set the variables the setter methods. while the code seems valid to me and should work perfectly, i get ArrayIndexOutOfBounds and StringIndexOutOfBounds and respectively lines 111 and 134. i'm am not the original author of this code, all i want is to get it to work fine.
1package de.kugihan.dictionaryformids.dictdconv;
2
3import java.io.FileOutputStream;
4import java.io.IOException;
5import java.io.OutputStreamWriter;
6
[code]....
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Apr 15, 2015
i need to change my code in order to stop the member variables from being directly altered and its been suggested that i should use a setter and getter method. Ive read up about these and im still unsure at how they should be implemented into my code for my project.
import ddf.minim.*;
DragShape[] piece =new DragShape[77];
PImage puz16;
PImage frame;
PImage text;
[code]....
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Jun 30, 2014
so, i was reading my java book and learning about objects and methods and it starts talking about Encapsulation and mentions that it's good practice to set instance variables as private and instead of accessing the instance variables directly, we should create a set method and get method to get and set the stuff we want to pass to the class containing the object...
for example, in this class, we're passing the integer 70 for object dog one and integer 8 for object dog two for the dog class... and these these 2 integers are sent to the setsize method so we're not accessing instance variable size directly.
i dont quite get it though....if we the programmer are the one deciding what size the integer is for the dog, and the setsize method takes the one.setSize(70) or (8) and puts them in setsize(int s) as s... but only to copy that integer stored in s back to private int size.... why do we even need to bother with making these two extra methods such as setSize, getSize?
in the book it says that... well what if the code gets into the wrong hand and someone writes something like one.setSize(0) then you would get a dog with size 0 which is essentially illogical. but then again, i'm the programmer, and i am the person who writes the code and passing the right integer.The reason for public and private... that part i understand... i can see why if a variable's data can get changed amidst the code during calculations and you dont want it to directly change the original variable and have it mess up the code, but this code from the book just a bad example of demonstrating the reason? since we manually pass the information ourselves and passing it to method setSize... and all setSize does is stores it in another integer, only to copy it right away to size (which is the original private variable we were tryign to protect?
Any simple code to demonstrate how the code might end up changing an instance variable and why we would want to protect it by using private?
class GoodDog {
private int size;
public int getSize() {
return size;
}
public void setSize(int s) {
size = s;
[code]...
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Jun 2, 2014
If I had this code:
<h:dataTable value="#{customer.customerList}" var="c"
styleClass="order-table"
headerClass="order-table-header"
rowClasses="order-table-odd-row,order-table-even-row"
>
And in the server getCustomerList() accessed to database, how many times getCustomerList() would be called from I request the xhtml page?. I have read this would be called several times because of JSF internals and It would be better to store it in a variable and access this variable.
1. Is this true this would be called several times? why?
2. If the previous statement was true, how to avoid it, I mean not call the method from a service?
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Feb 19, 2011
I thought static methods could never use instance variables, because they wouldn't know which instance to look at.
From Head First Java, p. 284: "A static method is not associated with a particular instance - only the class - so it cannot access any instance variable values of its class. It wouldn't know which instance's values to use."
Now I was answering some mock exam questions from Cameron McKenzie's SCJA book, and I don't understand one of the options. On page 205, the last question has an option that says: "Instance variables ... are not visible in static methods, unless passed in as arguments." This option is supposed to be correct. Now... how does that work?
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Jan 15, 2015
a. Create an application named ArithmeticMethods whose main() method holds two integer variables. Assign values to the variables. In turn, pass each value to methods named displayNumberPlus10(), displayNumberPlus100(), and displayNumberPlus1000(). Create each method to perform the task its name implies.
b. Modify the ArithmeticMethods class to accept the values of the two integers from a user at the keyboard.
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Mar 1, 2015
Does child class gets a copy of the methods and variables of parent class?
public class test1 {
public static void main(String a[]) {
Child c = new Child();
c.print();
[Code] ....
why is the output 1?
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Jan 22, 2015
when i try to compile following source file, there is a error which states "MovieTestDrive is public, so must be declared in a file MovieTestDrive.java" i didnot understand. i am beginner in java;
class Movie
{
String title;
String genre;
int rating;
void playit()
{
System.out.println("playing the movie");
}
}
public class MovieTestDrive
[code]....
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Oct 23, 2014
Each time i create a new project or try to compile my workflow (run as GenerateDemo.mwe2 file by write clicking on the file the run as --> WME2 Workflow) it prompts the error I've attached the picture of.
What is it for? How can i get rid of it?
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Feb 8, 2015
I tried running this program but shows some compilation error of cannot find symbol . in following:
p1.num, p2.num and p3.num
cass Guessgames
{
void startgame()
{
Players P1=new Players();
Players P2=new Players();
Players P3=new Players();
boolean p1isright=false;
boolean p2isright=false;
boolean p3isright=false;
int guessp1=0;
[code].....
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Dec 24, 2014
I've a .java file that won't compile, but produces no errors (in cmd prompt).
I think its the import of java.util.ArrayList thats causing the problem (because it can compile a different file in the same source folder) - so i'm assuming its the classpath that is wrong. which is fine. i love fighting with classpaths.
But why isn't it providing me with an error. the compiler usually goes bat-sh.. crazy if the -cp is incorrect!
Its because I'm switching between command prompt and a text editor and it hadn't saved the file for some reason, and still won't am getting rid of this editor!!
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Jun 5, 2014
Am facing a very strange issue. While trying to compile a very simple Hello World java program, the compilation completes successfully without any error or warning, but it does not generate the class file.
It happens when I compile with a particular jar file, otherwise compiling only the program (or with any other jar) does generate the class file. I am using java 1.7.0_45.
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May 5, 2014
I want to know if there is any general rule/pattern about things which give compilation fails and things which go for Runtime error/exception. OR only way is to remember all of them and there is no actual pattern in it.
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Nov 29, 2014
I'm having some difficulty getting this GUI dice game to compile. I'm using javac and notepad++ for this and I'm getting the following errors:
DiceGame.java:34: error: cannot find symbol
die2label = new JLabel();
^
symbol: variable die2label
location: class DiceGame
[Code] ....
4 errors
My code is as follows:
import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;
public class DiceGame extends JFrame
[Code] ....
I'm sure the problem is something trivial, but I guess that's all part of the learning process that I have to go through.
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Mar 17, 2014
We are getting "Code too large" compilation error for one of our class. This class contains public String fields for label ID and value. We use this class for localization, except for English all other language labels come from .properties files.
The reason we are getting this error is because we have a static block in which using reflection we are populating a HashMap with all public fields and their value. The number of fields have gone up to the extinct where we are crossing the 64K limit for a static method. One of the most feasible solution was to use .properties files for English labels as well.
I will be calling this class MyLabels. We defined a super class for MyLabels called MyLabelsExt. And now we are adding labels into the super class instead of the MyLabels. By running some tests we confirmed that the map that we initialize in MyLables class contains all the fields from both MyLabels and MyLabelsExt class.
How is the 64K limit error not coming if the labels are defined in a super class. Does that mean Java is able to identify that some of the fields are coming from parent class, and that is being treated as separate from the child class. And how is the map that we initialize having all the value.
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Apr 20, 2014
I have a simple doubt
float k = 0;
k+=0.2;
k=k+0.2; // here compilation error
compliation error Type mismatch: cannot convert from double to float
My question is why not a complilation error at k+=0.2;
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Feb 14, 2014
I was doing coding exercise from a book ('OCP Java SE 6 - Practice Exams' by Kathy Sierra and Bert Bates). I came to a question that told to demonstrate the difference between 'default' and 'protected' access rules by creating/making a directory structure and putting a couple of classes in different packages.
For this, I made a total of four classes, out of which, three classes are-Car, TestingCars, CarDimensions. (The fourth is not yet used in testing code till now, so, I am giving only the other three classes.) Their coding is given below.
Out of these classes, the classes- TestingCars and Car - are in a directory (say, FolderName). And, the class- CarDimensions is in FolderName's sub-folder.
The class 'CarDimensions' is public (and its components too are public). And, I am testing all the classes from the class- 'TestingCars'. But, this class (TestingCars) is not able to find the public class- 'CarDimensions' which is in its sub-folder and gives two 'Cannot find symbol' errors citing the class-CarDimensions. Also, If all three classes are put in one single directory, the programs work, without any error.
Coding:
Class TestingCars:class TestingCars {
public static void main(String[] args) {
Car c = new Car();
c.setType("FourWheeler");
[Code]....
I could not find why the public class- CarDimensions- is not getting found by the TestingCars class.
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Mar 30, 2014
Let's get it out of the way -- I'm stumped. On something that should be pretty simple to solve. Code follows.
public class Sum {
public static void main(String [] args) {
Double nSum = 0.0;
Double aDouble = 100.0;
for (int i = 0; i < 1000; i++){
nSum += 0.1;
[Code] ....
The output:
100.000000
100.000000
false
false
false
false
false
Process finished with exit code 0
I wrote another simple program and hardcoded the values: aDouble = 100.0; bDouble= 100.0000
Using aDouble.equals(bDouble) returns true, just as one would expect.
So what am I overlooking?
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Feb 25, 2014
Having two values
<c:set var="var1" scope="view" value="#{ID1}"/>
<c:set var="var2" scope="view" value="${ID2}" />
I tried in <c:if test=${var1 == var2}>
and eq also
above condition is not working. Both are same object. How to check?
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Apr 8, 2014
New to java/programming and i cant understand why the pen variable does not display the the correct value ... For example for input 1 ; 2 ; 3 ; 4 both variables will display 10 and i dont understand why pen does not have the value 6 .
import acm.program.*;
public class Chap4_ex12 extends ConsoleProgram {
public void run () {
int pen = 0;
int r = 1;
int sum = 0;
while (r !=SANTINEL) {
r = readInt(" ? ");
pen=sum ;
[code].....
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Jan 21, 2015
Variables defined in interface are public static and final so I was thinking that we should not be able to override the variables in a class thats implementing the interface. But when I am compiling the below class, it compiles fine and gives the correct values. but when I did disp.abhi = 35; it gives a compile error (cannot override final variable)
interface display{
int abhi = 10;
void displayName();
[code]....
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Jun 24, 2014
This is my first time working with C++ and I have put together this program and came up with two errors and I am unsure what it is wanting me to do. The errors I got are:
1>c:usersownerdocumentsvisual studio 2010projectsweek5week5passing_by_value.cpp(30): error C2064: term does not evaluate to a function taking 1 arguments
1>c:usersownerdocumentsvisual studio 2010projectsweek5week5passing_by_value.cpp(38): error C2064: term does not evaluate to a function taking 1 arguments
#include<iostream>
using std::cin;
using std::cout;
using std::endl;
//initialize arrays
int incr10(int* numa,int* numb);
[Code] ....
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Apr 13, 2014
I am new in this programming language, java. I have a problem after I set my path ";C:Program Files (x86)Javajdk1.7.0_51in". I made a simple program but an error occurred. Here's the screenshot.....
Attached image(s)
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