Java

Re: Object parsing non-static

20-Aug-12 23:11

From my understanding so far from the Java tutorials, but there was a question I wanted to clarify.
When creation of a Object which isn't static, each decleration of the object with Object object = new Object() will create a new instance,
if it was static wouldn't that mean instead of creating multiple instances, instead of only existing as one instance. As a non static would they then be independent of each other?

public class One{
    Object object = new Object();

    public static void main(String[] args){
    One.start(object);
    }
}
public class Two{
    Object obj = new Object();
    public void start(Object obj){
        this.obj = obj;
    }
}

Nagy Vilmos21-Aug-12 6:48

Nagy Vilmos

21-Aug-12 6:48

Your understanding is a bit off.

There is no such thing, in Java at least, as a static object. There are classes with static only methods, so no instances are required, and there are singletons, classes which only ever have a single instance.

Each class defines a type of object and how it works, it is not the object itself. Within a class, you can have items defined as static. Static members are shared by all instances of the class and do not actually require an instance to be created; a good example is the main entry method.

Re: Object parsing non-static

jschell21-Aug-12 8:40

jschell

21-Aug-12 8:40

Joshhua123 wrote:
When creation of a Object which isn't static, each decleration of the object
with Object object = new Object() will create a new instance,

You can have static and non-static member variables. If you have non static member variable as per your example then for each instance of 'One' that you create then the member variable for that instance will point to a different instance of Object.

Joshhua123 wrote:
if it was static wouldn't that mean instead of creating multiple instances,
instead of only existing as one instance.

If the member variable was static then there would be only one instance of Object regardless of how many new instances of 'One' you created.

Joshhua123 wrote:
As a non static would they then be independent of each other?

As noted above (when it is a non-static member) there is a new Object created each time. They are different so yes they are independent.

Is it a bug or featuere

Amarap18-Aug-12 0:58

Amarap

18-Aug-12 0:58

In this code
int i =2;
System.out.print(" Run " + i+1 + " ");

It prints Run 21
Where I would have expected to print Run 3

Amara

'Now I understand how stupid I am, thanks for everybody's contribution.

modified 18-Aug-12 18:54pm.

Manfred Rudolf Bihy18-Aug-12 2:11

Manfred Rudolf Bihy

18-Aug-12 2:11

The plus operator is left associative so I'd expect 21 as the result. 22 does not make any sense whatsoever. What happens when you put i + 1 in parenthesis like this: (i + 1).

Try that and think about associativity of operators and what it means to the process of evaluation/compilation.

Cheers!

"With sufficient thrust, pigs fly just fine."

Ross Callon, The Twelve Networking Truths, RFC1925

Gerben Jongerius18-Aug-12 2:12

Gerben Jongerius

18-Aug-12 2:12

The reason you are not getting 'Run 3' is because Java is thinking about string concatination. As it is processing from left to right you would see:

"Run 2" + 1 + ""

But this is where it gets a bit strange, I would expect to see the number 1 printed next giving you:

"Run 21"

If you want to add two numbers you must use brackets to indicate priority:

System.out.print("Run "+ (i+1));

Eddy Vluggen18-Aug-12 2:28

Eddy Vluggen

18-Aug-12 2:28

..if the system had these kind of "bugs" or "features", they would have been found by now, don't you think? Smile | :)

Re: Is it a bug or featuere

TorstenH.18-Aug-12 3:22

TorstenH.

18-Aug-12 3:22

The others have already explained why it is so.

I would like to add into, that the + is an operator and is overloaded in the String class and also used different in the System.out.

Operators in Java[^]

regards Torsten
When I'm not working

Gowtham Gutha15-Nov-12 7:25

Gowtham Gutha

15-Nov-12 7:25

int i =2;
System.out.print(" Run " +(i+1)+ " ");

This is the code. Keep the brackets.

Gowtham Gutha (Java-Demos.Blogspot.Com)

problem while updating a file

Namdeo Badhe17-Aug-12 7:07

Namdeo Badhe

17-Aug-12 7:07

suppose i have a text file as data.txt has following content such as

12.12.12.12 "www.google.com"|"www.yahoo.com"|"www.rediffmail.com"
13.13.12.12 "www.yahoo.com"|"www.rediffmail.com"|"www.google.com"|"www.google.com"
14.14.12.12 "www.yahoo.com"|"www.rediffmail.com"|"www.yahoo.com"

i have another text file as token.txt has following content such as

"www.google.com" 100
"www.yahoo.com" 200
"www.rediffmail.com" 300

i want to make new file as result.txt that should contain the following data such as

12.12.12.12 100 200 300
13.13.12.12 200 300 100 100
14.14.12.12 200 300 200

my code is as follows

import java.util.*;
import java.io.*;

public class UpdateFile
{

public static void main(String[] args) throws Exception
{

BufferedReader in=new BufferedReader(new FileReader(new File("data.txt")));
PrintWriter out=new PrintWriter(new FileWriter(new File("result.txt")));

String str="";

while((str=in.readLine())!=null)
{
ArrayList<string> url=new ArrayList<string>();
StringBuilder sq = new StringBuilder();
String parts[]=str.split("\\s+");

BufferedReader in2=new BufferedReader(new FileReader(new File("token.txt")));

String str2="";

String matchstr= parts[1];

String mm[]=matchstr.split("\\|");

for(int h =0;h<mm.length;h++){
while((str2="in2.readLine())!=null){
" string="" urltoken[]="str2.split("\\s+");
" if(mm[h]="=" null="" ?="" urltoken[0]="=" :="" mm[h].equals(urltoken[0])){

="" if(urltoken[1].tostring()!="null){
" url.add(urltoken[1].tostring()+"?");
=""
="" }
="" url.add(str2);
=""

="" if(url.size()="">0)
out.print(parts[0]+" "+" ");

for(int i=0;i<url.size();i++)
{
="" if(url.size()="">0)
{

out.print(url.get(i));

}}

url.clear();
out.println();
out.flush();

}

}
}

double post

TorstenH.17-Aug-12 9:00

TorstenH.

17-Aug-12 9:00

double post

please answer here-> code for project work[^]

regards Torsten
When I'm not working

problem while updating a text file in java

Namdeo Badhe17-Aug-12 6:45

Namdeo Badhe

17-Aug-12 6:45

uppose i have a text file as data.txt has following content such as

12.12.12.12 "www.google.com"|"www.yahoo.com"|"www.rediffmail.com"
13.13.12.12 "www.yahoo.com"|"www.rediffmail.com"|"www.google.com"|"www.google.com"
14.14.12.12 "www.yahoo.com"|"www.rediffmail.com"|"www.yahoo.com"

i have another text file as token.txt has following content such as

"www.google.com" 100
"www.yahoo.com" 200
"www.rediffmail.com" 300

i want to make new file as result.txt that should contain the following data such as

12.12.12.12 100 200 300
13.13.12.12 200 300 100 100
14.14.12.12 200 300 200

my code is as follows

import java.util.*;
import java.io.*;

public class Remove
{
public static void main(String[] args) throws Exception
{
BufferedReader in=new BufferedReader(new FileReader(new File("C://find token//output.txt")));

PrintWriter out=new PrintWriter(new FileWriter(new File("C://find token//WASD.txt")));
//BufferedReader in=new BufferedReader(new FileReader(new File("C://find token//Nasa File Data//output.txt")));

//PrintWriter out=new PrintWriter(new FileWriter(new File("C://find token//Nasa File Data//WASD.txt")));

String str="";
while((str=in.readLine())!=null)
{
ArrayList<string> url=new ArrayList<string>();
String parts[]=str.split("\\s+");

BufferedReader in2=new BufferedReader(new FileReader(new File("C://find token//tokenfile.txt")));

String str2="";
//char []n= new char[27];
while((str2=in2.readLine())!=null)
{
String urltoken[]=str2.split("\\s+");
if(parts[1].indexOf(urltoken[0].toString())!=-1)

{
if(urltoken[1].toString()!=null)
url.add(urltoken[1].toString()+"?");

}

}

if(url.size()>0)
out.print(parts[0]+" "+" ");

//System.out.println(url.size());
for(int i=0;i<url.size();i++)
{
="" if(url.size()="">0)
{

out.print(url.get(i));

}}

in2.close();
url.clear();
out.println();
out.flush();
//}

}System.out.println("WASD is Created");
}
}

Re: problem while updating a text file in java

Richard MacCutchan17-Aug-12 6:59

Richard MacCutchan

17-Aug-12 6:59

This is a repost of code for project work[^], which has already received some suggestions. If you want further help then please edit this question and put your code between <pre> tags for readability. Also, please explain what problems you are having with your code.

One of these days I'm going to think of a really clever signature.

Message Removed

16-Aug-12 6:53

Member 9362321

16-Aug-12 6:53

Message Removed

Swing

Joshua Waring15-Aug-12 23:53

15-Aug-12 23:53

First lets give some context, I've just created a client and server but they don't work without using console So I've decided to create a GUI on top they'll communicate though the Stack, but that's all for a later date, right now I get a error on the Even listener which says that the JTextField is empty upon .getText() even though it's not. I've looked though it, but since I'm quite new to the whole Swing field, it's a challenge for me to fix the problem. It really is a simple GUI.

Java

import java.awt.Button;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;

import javax.swing.*;
public class GUI extends JFrame implements ActionListener{
	Stack<String> incoming = null;
	Stack<String> outgoing = null;
	JTextField input;
	JTextArea output;
	Button button;
	public GUI(){
		
		setTitle("Satire v1.0.1");
		setSize(320,360);
		setLocationRelativeTo(null);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		
		JPanel panel = new JPanel();
		panel.setLayout(null);
		
		output = new JTextArea();
		output.setBounds(0, 0, 300, 300);
		output.setEditable(false);
		
		input = new JTextField();
		input.setBounds(0, 300, 260, 20);
		
		button = new Button("SEND");
		button.setBounds(250, 300, 50, 20);
		button.addActionListener(this);
		
		getContentPane().add(panel);
		panel.add(button);
		panel.add(input);
		panel.add(output);
	}
	public void actionPerformed(ActionEvent e) { 
		GUI gui = new GUI();
		try{
			String out = gui.input.getText();
			gui.input.selectAll();
			outgoing.add(out);
		}catch(NullPointerException e3){}
		gui.output.append(outgoing.pop());
	}
	
	public static void main(String[] args){
		 SwingUtilities.invokeLater(new Runnable() {
			 public void run(){
				 GUI cGUI = new GUI();
				 cGUI.setVisible(true);
			 }
		 });
	}
}

pasztorpisti16-Aug-12 0:28

pasztorpisti

16-Aug-12 0:28

You are new to object oriented programming as well, arent you? Smile | :)

Instead of this:

Java

public void actionPerformed(ActionEvent e) {
    GUI gui = new GUI();
    try{
        String out = gui.input.getText();
        gui.input.selectAll();
        outgoing.add(out);
    }catch(NullPointerException e3){}
    gui.output.append(outgoing.pop());
}

Use this:

Java

public void actionPerformed(ActionEvent e) {
    try{
        String out = input.getText();
        input.selectAll();
        outgoing.add(out);
    }catch(NullPointerException e3){}
    output.append(outgoing.pop());
}

Joshua Waring16-Aug-12 0:45

16-Aug-12 0:45

I have made the edit, yes I'm new, but learning fast, a lot faster than expected.
though the edit has been made, there was no change to the error. What I don't understand is that the field isn't empty D:

pasztorpisti16-Aug-12 0:55

pasztorpisti

16-Aug-12 0:55

There you go. This time I compiled/tested it, contained another big mistake. Why have you used those stacks? You should check the error messages as well in the console output!!! You program threw exceptions!

Java

import java.awt.Button;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Stack;
 
import javax.swing.*;
public class GUI extends JFrame implements ActionListener{
	JTextField input;
	JTextArea output;
	Button button;
	public GUI(){
		
		setTitle("Satire v1.0.1");
		setSize(320,360);
		setLocationRelativeTo(null);
		setDefaultCloseOperation(EXIT_ON_CLOSE);
		
		JPanel panel = new JPanel();
		panel.setLayout(null);
		
		output = new JTextArea();
		output.setBounds(0, 0, 300, 300);
		output.setEditable(false);
		
		input = new JTextField();
		input.setBounds(0, 300, 260, 20);
		
		button = new Button("SEND");
		button.setBounds(250, 300, 50, 20);
		button.addActionListener(this);
		
		getContentPane().add(panel);
		panel.add(button);
		panel.add(input);
		panel.add(output);
	}
	public void actionPerformed(ActionEvent e) { 
		try{
			String out = input.getText();
			output.append(input.getText());
			input.selectAll();
			input.requestFocusInWindow();
		}catch(NullPointerException e3){}
	}
	
	public static void main(String[] args){
		 SwingUtilities.invokeLater(new Runnable() {
			 public void run(){
				 GUI cGUI = new GUI();
				 cGUI.setVisible(true);
			 }
		 });
	}
}

Joshua Waring16-Aug-12 1:22

16-Aug-12 1:22

the purpose of the stack was for when I implements it into my chat client I'll have something to send it by, without changing the code around too much. I personally don't see how it caused an error.