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
}
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
I am having hard time to grasp the concept of java as i am beginner. according to different sources found in internet, only one class is written in one source file. and all those class can be accessed through the main class.
my question is
1.can we access one class present in one source file, through another class present in another source file [not through the class containing main method]?
2.can we create more than 1 class in same source file?is there special way to do it? i do get error always when i try to do so
3.can multiple classes contain main method? or should there be only single class containing it?
Does a variable have public access modifier? if we can use it within the class and outside of the class then can i access a public variable as follows??
class mo
{
void display() {
public int a=9;
System.out.println(a);
}
public static void main(String[] args) {
mo m=new mo();
m.display();
}
}
ERROR:
It shows 6 errors :-O.
Error 1. illegal start of the expression
2. class,interface, or enum expected
I'm having difficulty understanding this small piece of code:
package food;
public abstract class Fruit {
private String color;
private String tasteType;
public void setColor(String color) {
this.color = color;
}
public abstract void setTasteType(String taste);
}
The above is an abstract class which describes the basic structure that every fruit should "extend".
The below is a concrete subclass of the Fruit class called Apple.
import food.Fruit;
class Apple extends Fruit {
public void setTasteType(String taste) {
tasteType = taste;
}
}
Also do note that the two pieces of code are in different packages!
Upon compiling the Apple class I get the following error:
Apple.java:4: error: tasteType has private access in Fruit
tasteType = taste;
^
What I don't understand is this: I've given a non-abstract implementation to the "setTasteType" method in the Apple class and clearly setTasteType should have the authority to modify the private instance variables of Fruit. But it turns out I'm wrong.
Why do we use public access modifiers with String toString() method in java while overriding???
View Replies View RelatedTo be specific, how can I use enumeration of one source-code file in another.
View Replies View Related "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.
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?".
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?
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.
I am new to threads, This is a project about 2048 game to be more accurate, and i want this project to run in this thread that i make in main...
My main:
public class Execute {
public static void main(String[] args){
Display d = new Display();
Shell s = new Shell(d);
Model m = new Game2048Model();
View ui = new Game2048View(m.getBoardArr(),d,s);
[Code] ....
And the error is:
Exception in thread "Thread-0" org.eclipse.swt.SWTException: Invalid thread access
at org.eclipse.swt.SWT.error(Unknown Source)
at org.eclipse.swt.SWT.error(Unknown Source)
at org.eclipse.swt.SWT.error(Unknown Source)
at org.eclipse.swt.widgets.Display.error(Unknown Source)
at org.eclipse.swt.widgets.Display.checkDevice(Unknown Source)
at org.eclipse.swt.widgets.Display.readAndDispatch(Unknown Source)
at view.Game2048View.run(Game2048View.java:55) //problem at Run
at java.lang.Thread.run(Unknown Source)
Here is the problem....
@Override
public void run() {
while(!shell.isDisposed()){
if(!display.readAndDispatch()){
display.sleep();
}
}
display.dispose();
}
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?
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!
I want to know if a java class name can be declared as "pack1.ClassName". I know the naming conventions rules. I know that this kind of names are not supposed to be used. But I am just curious of whether Java accepts such kind of names also i want to know if $ClassName, _ClassName are valid for classname and are the being used anywhere in the application development.
View Replies View RelatedI'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] .....
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?
So I'm not entirely sure what to name my packages. Sometimes I have to many and it becomes overwhelming. Sometimes I don't have enough and I cannot keep my files organized. What is a good naming convention for Java packages?
View Replies View RelatedThe naming conventions for coding Java applications are clear to me. I'm wondering what the best practices are for naming Java projects e.g. when creating a new project in NetBeans IDE or in BitBucket?
View Replies View RelatedI 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.
View Replies View RelatedI have a requirement where I have to send a file from a local system to unix box(present on client side) using java code.I have developed a code that is successfully sending the file from local system to client side unix box (I am connecting to client side unix box using VPN) provided I run the code in my eclipse IDE present in local system. But when I am running the same code in the unix box it is throwing null pointer exception.Might be the unix system is not recognising the local system. Please find the code.
package abc;
import java.io.File;
import java.io.FileInputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.Properties;
import com.jcraft.jsch.Channel;
[Code] ....
Error on unix box which I am getting is :-
Inside sftpConnection method
llllllll
fffffffffffff
Connection Successfull
Channel Connection Succesfull
aaaaa
Inside findFile method
Exception in thread "main" java.lang.NullPointerException
at abc.TranferFile.sftpConnection(TranferFile.java:58)
at abc.TranferFile.main(TranferFile.java:21)
I am getting an error as follows while trying to compile a java file for servlet:-
"error while writing BeerSelect: WEB-INFclassesBeerSelect.class (Access is denied)
public class BeerSelect extends HttpServlet
^
1 error"
I am using "C:Program FilesApache Software FoundationTomcat 8.0webappsBeerBottlejavac -d WEB-INFclasses BeerSelect.java" to compile the file.
I am using Windows 8.1
I want to access variable of java file into jsp Page. So I tried to do this but it does not work.
Problem : when I am trying to access "getName" method of java class into jsp file it displaying error, i already imported "Ajaxmethod.java" file in to "success.jsp" I want to access "getName" method in to jsp file without creating object of class.
Ajaxmethod.java
package a.b;
public class Ajaxmethod implements Action{
public String name;
public String getName() {
return name;
}
[Code]...
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]...
This is a snippet code that im developing. (no source of it) . I am facing a trouble to extract file in the same directory as the source file (example: extract here option)
public class HelperAction {
public static void unzip(String zipFilePath)throws IOException {
File dir = new File(zipFilePath.substring(0,zipFilePath.length()));
// create output directory if it doesn't exist
if(!dir.exists()) dir.mkdirs();
FileInputStream fis;
[Code] ....
I have a file(source.txt) that contains some texts. Now, the java code is to run through each line in the source file and check if that line begins with a number and if true, copy that line to the destination file(destination.txt). I have the code but I am not sure why I can't loop through each line in the source.txt file. Below is my java code:
public static void copyFile(File source, File destination) {
BufferedReader br;
try {
FileWriter fw = new FileWriter(destination.getAbsoluteFile());
PrintWriter bw = new PrintWriter(fw);
br = new BufferedReader(new FileReader(source));
String line = new String();
[Code] ....
As shown in the source.txt file, there are 4 lines in the file but when the execution gets to while ((line = br.readLine()) != null) , it executes to false.. Why this is so?
below is the source.txt file
12 is a number
Green is bad
5 is not so cool
you are right