My first Java Program

I will be taking Java in School in a couple of months. I thought it would be a good idea to start trying it out now. One of the books I am reading has this example problem. It basically wants you to draw a hollow square 5 by on the screen. It says to use a while loop and if statements to solve. I don't no where to start, any help/advice would be great.
Thanks

The Book "Thinking in JAVA" is a great way to learn the language. The Book is really usefull and explains alot of ideas and concepts.
Plus its free so you can download it
http://www.mindview.net/Books/TIJ/
Good Luck!

Similar Messages

My first java program!! ALMOST done..I hope

I've just written my first java program (part of a class I'm taking).. It's feeling kinda awkward since I'm a C++ programmer.. I've written most of the code but I'm still having problems and I thought I should show it to you to get some help..
import java.lang.*;
import java.util.*;
public class Dice
private static Random generator = new Random();
int Die1, Die2, rolled, pairNum, pairSum;
public Dice()
   int[] Dice_arr={Die1, Die2};
   new Random(System.currentTimeMillis());
   return;
}//end_func_Dice
   public static roll()
     rolled = generator.nextInt(6) + 1;
     return rolled;
    }//end_func_roll
   public String toString()
     StringBuffer bfr = new StringBuffer("\n");
     System.out.println("Rolling Dice...");
      for(pairNum=0; pairNum==10; pairNum++)
        System.out.println("Pair"+pairNum+": "+Die1+","+Die2+" Sum= "+pairSum);
       }//end_for_
    }//end_func_
}//end_class_Dice
public static void main(String args[])
      for (int dieNum=0; dieNum==2; dieNum++)
        Dice.roll();
        Dice_arr[dieNum]=rolled;
       }//end_for_
     return;
    }//end_func_mainI need main to instatiate the Dice class and then use the toString to print the dice numbers and their sum 10 times..
I hope this doesn't need much effort,
Thanks a bunch in advance..

Right now, my opinion in java is that it's too
complicated for no reason compared to C++..It's not too complicated, it's just that you are new at this.
Here's a little example of a simple class with a simple main method, the rest figure it out yourself, and with time read some java books, you won't learn java just by knowing C++.
public class Human {
    // See this as C constants (although they're not their Equivalent)
    public static boolean MALE = true;
    public static boolean FEMALE = false;
    //member variables.
    private String name;
    private boolean sex;
    /** Creates a new instance of Human */
    public Human(String n, boolean s) {
        name = n;
        sex = s;
    }//End of CONSTRUCTOR.
    public String getName() {
        return name;
    }//End of getName
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("[Name: " + name);
        if(sex)
            sb.append(", sex: Male]");
        else
            sb.append(",sex: Female]");
        String returnValue = new String(sb);
        return returnValue;
    }//End of toString()
    //Just the main program, it could be at another class.
    public static void main(String[] args) {
        Human h = new Human("Pablo", Human.MALE);
        String theHumanAsAString = h.toString();
        System.out.println(theHumanAsAString);
    }//End of main method
}//End of class

Trying to compile my first Java program !

Hi,
I am a new programmer.Looking to clarify a very simple doubt while compiling my first java program.
I have set up jdk in the following directory on my PC , E:\j2sdk1.4.1_01\bin.
Now when I create the first AClass.java file in the AClass directory under bin and try and compile it I get the following error.
E:\j2sdk1.4.1_01\bin>java E:\j2sdk1.4.1_01\bin\AClass\AClass
Exception in thread main
java.lang.NoClassDefFoundError: E:\j2sdk1/4/1_01\bin\AClass\AClass
Kindly help me how to fix this.

hi,
Just do this,
set path & classpath either in the system environment veriable or in the command prompt as shown below.
set PATH=%PATH%;E:\j2sdk1.4.1_01\bin
set CLASSPATH=%CLASSPATH%;.
Be careful, there is a trailing DOT (.) at the end of the classpath, and that is what needed for
the JVM to find the class file. with this you would be able to run your program. Infact JDK1.4.x and higher
doesn't requires classpath to be set, your system classpath variable needs a DOT (.)
at the end of the classpath variable defined in the environment variable section of your computer or
in the command prompt you need it to set it once for the current command prompt window before
executing any java program.
Regards
Goodieguy

My first java programming - Need some help please!!!

I have to create a simple java program which i am not good at i am ok in C but my java is quite bad. The program need to define a class called Student and with a string called StudentNAme, a integer StudentID(key), An array of 8 integers called Marks that holds the students marks for 8 modules. It also says Include appropriate accessors, mutators and constructor(s) as well as a method to update the student�s marks. Anybody please help me in this question. I prefer an simple example of this program so I can learn faster, I dont even know how to declare a class.. So sorry but please help me out and thanks in advance

I would also suggest you try using an IDE like
eclipse (free)
www.eclipse.org
This will help you get a working program much faster.But please do also tell them that if they have troubles using it, they're supposed to read the IDE manual instead of posting here.

Error Message when running first java program

Hi,
I am reading "Sams Teach Yourself Java 6 in 21 Days" by Rogers Cadenhead. I am having a problem with compiling the sample program in the first part of the book, "HelloUser" which is supposed to print out "Hello (my name - Matt)" when run in the command line.
I receive this error when trying to run it after having successfully compiled it (I enter java HelloUser while in correct folder):
Exception in thread "main" java.lang.NoSuchMethodError: main
I have correctly set the PATH and CLASSPATH settings for my PC (Windows XP). I am guessing that I need to define a "main" or something. I'm brand new to Java but am good with the scripting language PHP. Please tell me what I should do to correct this problem. Thanks in advance

Here is the code for the program:
public class HelloUser {
     public static void man(String[] arguments) {
          String username = System.getProperty("user.name");
          System.out.println("Hello " + username);
}Here is what I enter in the Command Line:
cd \JavaWork\j21work
javac HelloUser.java
java HelloUser
There are no problems up until I enter the last line (java HelloUser) to run the program. By the way, I using JDK 6 update 1 with Windows XP.

My first java program. Design improvements?

Hello all,
I'm new to this forum (just joined today) so hi! I've been learning java for the last few months by reading a few books, and finally decided to take a crack at my first program (beyond hello world). This one is windows only. At work with a co worker we found that in windows 2000 the background images could get out of sync, so this program gives the user an alternative way to set the backgrounds.
What I'm asking is if anyone has any time to kill and enjoys reading source code to take a look at it for me. If you see any issues with how the program was implemented and could be improved please let me know.
Here's the link to the src: http://will.willandnikki.com/projects/bgchanger/BGChanger_src.zip
Here's a link to my jar:
http://will.willandnikki.com/projects/bgchanger/BGChanger.jar
Thanks,
Will

Right now, my opinion in java is that it's too
complicated for no reason compared to C++..It's not too complicated, it's just that you are new at this.
Here's a little example of a simple class with a simple main method, the rest figure it out yourself, and with time read some java books, you won't learn java just by knowing C++.
public class Human {
    // See this as C constants (although they're not their Equivalent)
    public static boolean MALE = true;
    public static boolean FEMALE = false;
    //member variables.
    private String name;
    private boolean sex;
    /** Creates a new instance of Human */
    public Human(String n, boolean s) {
        name = n;
        sex = s;
    }//End of CONSTRUCTOR.
    public String getName() {
        return name;
    }//End of getName
    public String toString() {
        StringBuilder sb = new StringBuilder();
        sb.append("[Name: " + name);
        if(sex)
            sb.append(", sex: Male]");
        else
            sb.append(",sex: Female]");
        String returnValue = new String(sb);
        return returnValue;
    }//End of toString()
    //Just the main program, it could be at another class.
    public static void main(String[] args) {
        Human h = new Human("Pablo", Human.MALE);
        String theHumanAsAString = h.toString();
        System.out.println(theHumanAsAString);
    }//End of main method
}//End of class

First Java Programming Assignment - Grad student needs Help

Thank-you to whomever helps me out here (I have been waiting for the Professor to respond for 2 days now, and our asignment is due by midnight 2-nite. Here is my problem. We have a value called nPer. This value is defined as a double (it needs to since, it perfoms lots of calculations). Now the assigment calls for the print line to display the field in its integer format. So I have done the following:
nPer=Math.ceil(nPer);
This has caused the value to be represented as 181.0. Not good enough! The value needs to be truncated and represented as 181.
The professor has provided us with directions that use the following syntax
(int)181.0
Putting that exact code in my program causes JBuilder to create an error message. Ergo, its not right. I have serached all over the tutorial looking for the proper method to resolve this, however - no luck. Could some kind sole please help??? Thank-you.

You can look at either java.math.BigDecimal, if the
true representation of the value and rounding are a
concern, or java.text.NumberFormat if it's simply a
matter of display.
Your professor must be an old C programmer. Casting a
double to an int? Oh, my. - MODBut that's what his assignment says, display it as an int. And the cast would work; I'm assuming he just didn't use it right.

Trying to get my first java program compile.

I just iinstalled j2sdk1.4.2_05 on Wind 98 and I have set the path variable in autoexec.bat and ran the .bat.
So, now the system recognizes the javac compiler but I am still not able to run a program Welcome.java
I created a Welcome.java file and stored it in C:\java\Welcome.java
I also set the sourcepath to sourcepath=c:\java; in my autoexec.bat file.
When I compile the following way, I get the following error:
c:\javac Welcome.java
Error: Cannot read: Welcome.java
Can anybody please tell me what I am doing wrong. Do i need to set any thing else.
Radhika.

I got it to compile and run....successfully.
Problem was- When I created the file Welcome.java in Notepad, it created with the following extension-
Welcome.java.txt. I renamed it to Welcome.java and it compiled and ran fine.
Thanks,
Radhika.

Programming your first java program, hello world

go here and do it quick and fun;
http://www.geocities.com/jon_riley/jon/java.htm

It is not visual, the same may we learned programming in class.I disagree. The tutorial may not have as big pictures as you have but it sure is visual:
http://java.sun.com/docs/books/tutorial/getStarted/cupojava/win32.html
Besides getting the thing done, it explains the common errors you could get, and applies to winNT and 2k (ME, anyone?) as well as win9x. Can you give any reason I should from now on recommend people using 32bit windoze to go to your page rather than the tutorial page?
By the way, who learned programming in class?

One more time, programming your first java program

go here;
http://jonjon.0catch.com
mirror site;
http://geocities.com/jon_riley/jon/java.htm

I must assume that your continued use of the forum as a signpost to your home page represents your lack of understanding of the "Terms of Use" agreement that you had to accept to be a member of the forum.
4.5 You agree not to use the Services for any unlawful activities not otherwise covered above, including (without limitation) attempting to compromise the security of any networked account or site, operating an illegal lottery or gambling operation, stalking, or making direct threats of physical harm. Additionally, You agree not to use the Services to:
(h) use Your My Sun account as storage for remote loading or as a door or signpost to another home page, whether inside or beyond Sun.com.
Other sections also apply.

My first Java program does;'t work HELP

I received the following message in the Command Prompt:Exception in thread "main" java.land.NoClassDefFoundError: Test
How do I fix this?
Source Code:
import java.awt.MediaTracker;
class Test {
public static void main(String[] args) {
for (int i = 0; i < args.length; i++)
System.out.print(i == 0 ? args[i] : " " + args);
System.out.println();

You might want to make your class public, although I don't think that's supposed to be necessary. It's most likely a classpath issue.
Instead of java Test, try java -cp . Test (Note the dot between -cp and Test.)
Javapedia: Classpath
How Classes are Found
Setting the class path (Windows)
Setting the class path (Solaris/Linux)
Understanding the Java ClassLoader
java -cp .;<any other directories or jars> YourClassNameYou get a NoClassDefFoundError message because the JVM (Java Virtual Machine) can't find your class. The way to remedy this is to ensure that your class is included in the classpath. The example assumes that you are in the same directory as the class you're trying to run.
javac -classpath .;<any additional jar files or directories> YourClassName.javaYou get a "cannot resolve symbol" message because the compiler can't find your class. The way to remedy this is to ensure that your class is included in the classpath. The example assumes that you are in the same directory as the class you're trying to run.

How to find that a java program is running for the first time on daily basi

it is like this
1. i will ran a java program every day and i have to find that it is running for the first time(as i may stop that program and may run again the same day )
Pls share ur ideas

san.kumar wrote:
it is like this
1. i will ran a java program every day and i have to find that it is running for the first time(as i may stop that program and may run again the same day )
Pls share ur ideasAs kajbj said - you need to store a token / file with a run date on the file system. Each time the application runs, have it compare with the date from this file with the current date. If different, it's the first run of the day. If not, it is not the first run of the day. Each time have it update the date on the file.

Running a java program a set number of times

This is a general question. Is it possible to make a java program run only 5 times for the sake of arguement.
Basically I want to write a program that will give the user some flexibility when it will actually run another Java program, but I only want them to be able to say "not now' for a set number of times. When the last time comes the other program will launch. I was initially thinking of the Do Whilw loop, but this needs to work when the program is restarted.
Program starts, it has 5 times it will run before it does something else(doesn't really matter now I think). User takes option "Not Now" and the program ends, but warns the user this will run 4 more times before you will need to do something.
This process will repeat until the user takes the option "Ok install now" or the time limit expires and the install occurs anyway. Can someone point me in the right direction.

ok I see so it's like one those programs that you download for free on the internet and they give you a set amount times to use it before you have to pay for it. but in this case when the number of times you use it equals 5 (or when the user clicks ok) a different java app will open automatically.
My first thought would be to Write a Serialized object to disk using objectOutputStream that stores the number of times the application has been opened. and each time the program runs it checks for the serialized object and then you can do something like what I posted before. of course if were worried about security the user could always look for the object and erase it, if so then I guess we would have to come up with another plan of attack
Hope this helps

Running a Java program on HP UX

Hi everyone
First time in life i have to make a Java program run on HP UX... the program is running perfectly in windows environment..... but when i copy the program to HP-UX and try to run it gives me following error
-----------------End Configuration-------------------------
Exception in thread "main" java.lang.NoClassDefFoundError: java/sql/Savepoint
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$1(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)
at oracle.jdbc.driver.OracleDriver.getConnectionInstance(OracleDriver.ja
va:468)
at oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:314)
at java.sql.DriverManager.getConnection(DriverManager.java:517)
at java.sql.DriverManager.getConnection(DriverManager.java:177)
at StatInterface.main(StatInterface.java:58)
I can guess that this has something to do with Class path or java home... i even don't know how to set paths in HP-UX
can u ppl help me?
Following are the details
OS Version = HP-UX rpsvr02 B.11.11 U 9000/800 (ta)
JVM = java version "1.3.1.02" Java(TM) 2 Runtime Environment, Standard Edition (build 1.3.1.02-011206-02:17) Java HotSpot(TM) Server VM (build 1.3.1 1.3.1.02-JPSE_1.3.1.02_20011206 PA2.0, mixed mode)
$PATH value
.:/home/express/bin:/home/express/bin:/home/express/BIN:/usr/local/bin:/opt/java1.3/bin:/home/oracle/product/9.2.0.1.0/bin:/usr/bin:/usr/ccs/bin:/usr/contrib/bin:/opt/mx/bin:/opt/hparray/bin:/opt/nettladm/bin:/opt/upgrade/bin:/opt/fcms/bin:/opt/pd/bin:/opt/resmon/bin:/usr/bin/X11:/usr/contrib/bin/X11:/opt/graphics/common/bin:/opt/scr/bin://opt/perl/bin:/usr/sbin/diag/contrib:/opt/hpnpl//bin:/usr/bin/X11:/usr/sbin:/opt/java1.3/bin
I really need your help.. and it is really urgent.. plz
Thanx in advance

In the documentation for Savepoint it states "since 1.4"
You need a more recent version of java. I suggest using asupported version like 1.4.2_08 or 1.5.0_04 if you can get them.
If not try getting the source for 1.6.0 and compiling it for HPUX.

Writing a java program for generating .pdf file with the data of MS-Excel .

Hi all,
My object is write a java program so tht...it'll generate the .pdf file after retriving the data from MS-Excel file.
I used POI HSSF to read the data from MS-Excel and used iText to generate .pdf file:
My Program is:
* Created on Apr 13, 2005
* TODO To change the template for this generated file go to
* Window - Preferences - Java - Code Style - Code Templates
package forums;
import java.io.*;
import java.awt.Color;
import com.lowagie.text.*;
import com.lowagie.text.pdf.*;
import com.lowagie.text.Font.*;
import com.lowagie.text.pdf.MultiColumnText;
import com.lowagie.text.Phrase.*;
import net.sf.hibernate.mapping.Array;
import org.apache.poi.hssf.*;
import org.apache.poi.poifs.filesystem.*;
import org.apache.poi.hssf.usermodel.*;
import com.lowagie.text.Phrase.*;
import java.util.Iterator;
* Generates a simple 'Hello World' PDF file.
* @author blowagie
public class pdfgenerator {
     * Generates a PDF file with the text 'Hello World'
     * @param args no arguments needed here
     public static void main(String[] args) {
          System.out.println("Hello World");
          Rectangle pageSize = new Rectangle(916, 1592);
                    pageSize.setBackgroundColor(new java.awt.Color(0xFF, 0xFF, 0xDE));
          // step 1: creation of a document-object
          //Document document = new Document(pageSize);
          Document document = new Document(pageSize, 132, 164, 108, 108);
          try {
               // step 2:
               // we create a writer that listens to the document
               // and directs a PDF-stream to a file
               PdfWriter writer =PdfWriter.getInstance(document,new FileOutputStream("c:\\weeklystatus.pdf"));
               writer.setEncryption(PdfWriter.STRENGTH128BITS, "Hello", "World", PdfWriter.AllowCopy | PdfWriter.AllowPrinting);
//               step 3: we open the document
                         document.open();
               Paragraph paragraph = new Paragraph("",new Font(Font.TIMES_ROMAN, 13, Font.BOLDITALIC, new Color(0, 0, 255)));
               POIFSFileSystem pofilesystem=new POIFSFileSystem(new FileInputStream("D:\\ESM\\plans\\weekly report(31-01..04-02).xls"));
               HSSFWorkbook hbook=new HSSFWorkbook(pofilesystem);
               HSSFSheet hsheet=hbook.getSheetAt(0);//.createSheet();
               Iterator rows = hsheet.rowIterator();
                              while( rows.hasNext() ) {
                                   Phrase phrase=new Phrase();
                                   HSSFRow row = (HSSFRow) rows.next();
                                   //System.out.println( "Row #" + row.getRowNum());
                                   // Iterate over each cell in the row and print out the cell's content
                                   Iterator cells = row.cellIterator();
                                   while( cells.hasNext() ) {
                                        HSSFCell cell = (HSSFCell) cells.next();
                                        //System.out.println( "Cell #" + cell.getCellNum() );
                                        switch ( cell.getCellType() ) {
                                             case HSSFCell.CELL_TYPE_STRING:
                                             String stringcell=cell.getStringCellValue ()+" ";
                                             writer.setSpaceCharRatio(PdfWriter.NO_SPACE_CHAR_RATIO);
                                             phrase.add(stringcell);
                                        // document.add(new Phrase(string));
                                                  System.out.print( cell.getStringCellValue () );
                                                  break;
                                             case HSSFCell.CELL_TYPE_FORMULA:
                                                       String stringdate=cell.getCellFormula()+" ";
                                                       writer.setSpaceCharRatio(PdfWriter.NO_SPACE_CHAR_RATIO);
                                                       phrase.add(stringdate);
                                             System.out.print( cell.getCellFormula() );
                                                       break;
                                             case HSSFCell.CELL_TYPE_NUMERIC:
                                             String string=String.valueOf(cell.getNumericCellValue())+" ";
                                                  writer.setSpaceCharRatio(PdfWriter.NO_SPACE_CHAR_RATIO);
                                                  phrase.add(string);
                                                  System.out.print( cell.getNumericCellValue() );
                                                  break;
                                             default:
                                                  //System.out.println( "unsuported sell type" );
                                                  break;
                                   document.add(new Paragraph(phrase));
                                   document.add(new Paragraph("\n \n \n"));
               // step 4: we add a paragraph to the document
          } catch (DocumentException de) {
               System.err.println(de.getMessage());
          } catch (IOException ioe) {
               System.err.println(ioe.getMessage());
          // step 5: we close the document
          document.close();
My Input from MS-Excel file is:
     Planning and Tracking Template for Interns
     Name of the Intern     N.Kesavulu Reddy
     Project Name     Enterprise Sales and Marketing
     Description     Estimated Effort in Hrs     Planned/Replanned          Actual          Actual Effort in Hrs     Complexity     Priority     LOC written new & modified     % work completion     Status     Rework     Remarks
S.No               Start Date     End Date     Start Date     End Date
1     setup the configuration          31/01/2005     1/2/2005     31/01/2005     1/2/2005
2     Deploying an application through Tapestry, Spring, Hibernate          2/2/2005     2/2/2005     2/2/2005     2/2/2005
3     Gone through Componentization and Cxprice application          3/2/2005     3/2/2005     3/2/2005     3/2/2005
4     Attend the sessions(tapestry,spring, hibernate), QBA          4/2/2005     4/2/2005     4/2/2005     4/2/2005
     The o/p I'm gettint in .pdf file is:
Planning and Tracking Template for Interns
N.Kesavulu Reddy Name of the Intern
Enterprise Sales and Marketing Project Name
Remarks Rework Status % work completion LOC written new & modified Priority
Complexity Actual Effort in Hrs Actual Planned/Replanned Estimated Effort in Hrs Description
End Date Start Date End Date Start Date S.No
38354.0 31/01/2005 38354.0 31/01/2005 setup the configuration 1.0
38385.0 38385.0 38385.0 38385.0 Deploying an application through Tapestry, Spring, Hibernate
2.0
38413.0 38413.0 38413.0 38413.0 Gone through Componentization and Cxprice application
3.0
38444.0 38444.0 38444.0 38444.0 Attend the sessions(tapestry,spring, hibernate), QBA 4.0
                                   The issues i'm facing are:
When it is reading a row from MS-Excel it is writing to the .pdf file from last cell to first cell.( 2 cell in 1 place, 1 cell in 2 place like if the row has two cells with data as : Name of the Intern: Kesavulu Reddy then it is writing to the .pdf file as Kesavulu Reddy Name of Intern)
and the second issue is:
It is not recognizing the date format..it is recognizing the date in first row only......
Plz Tell me wht is the solution for this...
Regards
[email protected]

Don't double post your question:
http://forum.java.sun.com/thread.jspa?threadID=617605&messageID=3450899#3450899
/Kaj

My first Java Program

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