Vectors

> The assignment I'm tring to do require me to use

> Vector objects with primitive data types. The chapter

> I read was very short will little examples.

Either you misunderstood your assignment or it's completely bogus. That is absolutely unequivocally impossible. You cannot ever have a Vector of primitive types.

Are you talking about an array?

kablaira at 2007-7-13 20:42:56 >

Well you've got a good start and it looks like more or less the right idea. You basically just want a loop that reads each number in and then iterates backwards over the Vector until it finds a number it's not bigger than or reaches the beginning, then insert it there.

I would start with getting a good clean loop for reading in each number. Right now you have a lot of code that looks like it is leftovers and can be deleted. I also see nothing to handle exceptions thrown.

kablaira at 2007-7-13 20:42:56 >

> There are loops that look back over a file,

> interesting.. I'll look in my textbook for that. The

> school book I have really sucks on examples.

Not over the file, over the Vector. But don't worry about that yet. Your loop that gets the numbers would look something like this:

for (int num = inFile.nextInt(); inFile.hasNext(); num = inFile.nextInt()) {

numberList.add(new Integer(num));

}

There's no error handling there. But that's probably beyond the scope of your assignment.

kablaira at 2007-7-13 20:42:56 >

Do it look better now?

import java.util.Vector;

import java.io.*;

public class BldList

{

public static void main(String[] args)

throws FileNotFoundException

{

Scanner inFile = new Scanner(new FileReader("Numbers.txt"));

PrintWriter outFile = new PrintWriter("Number.out");

Vector<Integer> numList = new Vector<Integer>(20);

int number;

boolean inserted = false;

System.out.println("Size: " + numList.size());

System.out.println("Capacity: " + numList.capacity());

number = inFile.nextInt();

numList.addElement (new Integer(number) );

//for (int loop = 1; loop < 20; loop++)

{

for(int index = 0; index < numList.size(); index++);

}

//for (int number = inFile.nextInt(); inFile.hasNext(); number = inFile.hasNext())

//{

//numList.add(new Integer(number));

//}

Integer temp = (Integer) listNum.elementAt(index);

if (temp.intValue() > number)

{

listNum.insertElementAt(new Integer(number), index);

inserted = true;

break;

}

if (!inserted) listNum.addElement(new Integer(number));

for (int count = 1; count < 20; count++)

System.out.println((Integer)numList.elementAt(count));

inFile.close();

outFile.close();

}

}

Raziela at 2007-7-13 20:42:56 >

When I run my code I get this:

-jGRASP exec: java BldList

Your sorted vector

42

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 2 >= 2

at java.util.Vector.elementAt(Unknown Source)

at BldList.main(BldList.java:40)

-jGRASP wedge2: exit code for process is 1.

-jGRASP: operation complete.

I'm reading in a text file with integers as such that must be sorted in the end:

42

468

335

1

170

225

479

359

463

465

206

146

282

329

462

492

496

443

328

437

What is stoping me for going through the list?

Raziela at 2007-7-20 23:57:36 >

sorry for the code button..

import java.util.Vector;

import java.io.*;

import java.util.*;

public class BldList

{

public static void main(String[] args)

throws FileNotFoundException

{

Scanner inFile = new Scanner(new FileReader("Numbers.txt"));

PrintWriter outFile = new PrintWriter("Number.out");

Vector<Integer> numList = new Vector<Integer>();

int number;

number = inFile.nextInt();

numList.addElement (new Integer(number));

//above line converts primitive int to an object and adds it to the vector

System.out.println("Your sorted vector\n");

/*to add the Integer objects in sorted order, you loop from 1 to 20: */

for (int insert = 1; insert < 20; insert++)

number = inFile.nextInt(insert);//reads it in

boolean inserted = false;

/* Use an inner loop to loop from 0 to numList.size(). In this loop you will compare each object in the vector

with the one you are trying to inset to find the proper positin for it*/

{

for (int loop = 0; loop < numList.size(); loop++)

number = inFile.nextInt();

Integer temp = (Integer) numList.elementAt(0);//retrieves Objeect at the position 'loop'

if (temp.intValue() > number) //compares number to the integer equivalent of temp

{

numList.insertElementAt(new Integer(number), 0); //inserts into corrrect place

inserted = true; // you've found it so set inserted to true

break;// break out of loop once number's been inserted

}

}

/* Once the for loop is done, check to see if you've inserted the item.

If not, it must be bigger than everything in the vector so insert it at the end*/

if (!inserted) numList.addElement(new Integer(number)); // adds at end

/*Once the vector has been populated in sorted order, then print it out usinf the

elementAt method. Use a for loop that iterates fron 1 to 20. Don't forget to cast it to an Integer

before printing.*/

for (int count = 1; count < 20; count++)

System.out.println((Integer)numList.elementAt(count));//To cast it to an integer and Print it out.

inFile.close();

outFile.close();

}

}

Raziela at 2007-7-20 23:57:36 >

You have some serious logic flaws in your code.

One such error is your trying to access some 20 elements of your vector, however, you only push one object into you vector.

Also your code formatting is very hard to read and follow. What are you tyring to do with that thing you call an inner loop-to-loop? Get rid of it..

Also Until you become a Java Zen master, always use the curly braces for any if, for, while, else, try/catch constructs in your code, even if you only have one statement. It will save you headaches in the long run.

I would highly suggest you download an integrated IDE such as Netbeans, Eclipse, or BlueJay and dump what ever your using now to edit your code.

Those will help you with keeping with current codeing standards.

Have fun!

JJ

Java_Jaya at 2007-7-20 23:57:36 >

I got it to print the corract amount of numbers but they are still not sorted yhey come out like this:

Your sorted values:

42

328

443

462

329

282

146

206

465

463

359

225

170

1

335

42

468

335

1

170

This is what I done to the code

import java.util.Vector;

import java.io.*;

import java.util.*;

public class BldList

{

public static void main(String[] args)

throws FileNotFoundException

{

Vector<Integer> numList = new Vector<Integer>(20);

Scanner inFile = new Scanner(new FileReader("Numbers.txt"));

int number;

number = inFile.nextInt();

numList.addElement(new Integer(number));

System.out.println("Your sorted values:\n" + number);

//above line converts primitive int to an object and adds it to the vector

/*to add the Integer objects in sorted order, you loop from 1 to 20: */

for (int x = 1; x < 20; x++)

{

number = inFile.nextInt();//reads it in.

//Also set a boolean variable called inserted to false.

boolean inserted = false;

/* Use an inner loop to loop from 0 to numList.size(). In this loop you will compare each object in the vector

with the one you are trying to insert to find the proper positin for it*/

for (int i = 0; i < numList.size(); i++)

{

Integer temp = (Integer)numList.elementAt(i);//retrieves Objeect at the position 'loop'

if (temp.intValue() > number) //compares number to the integer equivalent of temp

{

numList.insertElementAt(new Integer(number), 0); //inserts into corrrect place

inserted = true; // you've found it so set inserted to true

break;// break out of loop once number's been inserted

}

}

if (!inserted) numList.addElement(new Integer(number)); // adds at end

else

numList.addElement(number);

}

/* Once the for loop is done, check to see if you've inserted the item.

If not, it must be bigger than everything in the vector so insert it at the end*/

/*Once the vector has been populated in sorted order, then print it out using the

elementAt method. Use a for loop that iterates fron 1 to 20. Don't forget to cast it to an Integer

before printing.*/

for (int order = 1; order < 20; order++)

{

System.out.println((Integer)numList.elementAt(order));//To cast it to an integer and Print it out.

}

inFile.close();

}

}

Raziela at 2007-7-20 23:57:36 >

Look at this snipit of code.

// Dont need the 20. Vectors grow Dynamically

Vector<Integer> numList = new Vector<Integer>();

Scanner inFile = new Scanner(new FileReader("f:\\Numbers.txt"));

int number = 0;

// Look at this while loop. Isnt it much cleaner and easier

// to understand?

while (inFile.hasNext()) {

// Read the number in

number = inFile.nextInt();

// The next 2 system prints are for debugging only

System.out.print("Adding " + number + " to the Vector. ");

System.out.println(

"The Vector size is: " + (numList.size() + 1));

// Put the number into the Vector

numList.addElement(new Integer(number));

// Do more Stuff if you need to...

}

Dont you think it is easier to read and follow?

JJ

Java_Jaya at 2007-7-20 23:57:36 >