help me to check this RandomNumber

[shana07]

I need help on my random number program.
It is supposed to generate 40 random numbers (large numbers). But I just get 10 numbers and the result text file is emptied ...please teach me.
Thanks

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

class RandomNumber 
{

  public static void main (String args[]) 
  {  
    int[] ndigits = new int[40];
    double x;
    int n;
    
   Random myRandom = new Random();
  
    for (int i = 0; i < 40; i++) 
    {
     	 ndigits[i] = 0;
   	} 
      	for (long i=1000000; i < 100000000; i++) 
    	{
            	 x = myRandom.nextDouble() * 10.0;
     	 n = (int) x;
     	 //count the digits in the random number
     	ndigits[n]++;
   		}
   		
   		try 
   		{ 			
    	FileWriter writer = new FileWriter("randomnumber.txt");
    	PrintWriter outFile = new PrintWriter(writer); 
    	    		  
  	  		for (int i = 0; i < 40; i++) 
  	  		{
     			      			 
     			System.out.println(i+": " + ndigits[i]);
     			outFile.println(i+": " + ndigits[i]);
     			 
      		}
      		      		
    	}
    	catch (IOException exc)
    	{
    		System.out.println("Can't write into this file");
    	} 
  }
  
}

[r035198x]

I need help on my random number program.
It is supposed to generate 40 random numbers (large numbers). But I just get 10 numbers and the result text file is emptied ...please teach me.
Thanks

import java.util.Random;
import java.io.*;
 
class RandomNumber 
{
 
public static void main (String args[]) 
{ 
int[] ndigits = new int[40];
double x;
int n;
 
Random myRandom = new Random();
 
for (int i = 0; i < 40; i++) 
{
	 ndigits[i] = 0;
	} 
	for (long i=1000000; i < 100000000; i++) 
	{
	 x = myRandom.nextDouble() * 10.0;
	 n = (int) x;
	 //count the digits in the random number
	ndigits[n]++;
		}
 
		try 
		{ 			
	FileWriter writer = new FileWriter("randomnumber.txt");
	PrintWriter outFile = new PrintWriter(writer); 
 
			 for (int i = 0; i < 40; i++) 
			 {
 
			System.out.println(i+": " + ndigits[i]);
			outFile.println(i+": " + ndigits[i]);
 
		}
 
	}
	catch (IOException exc)
	{
		System.out.println("Can't write into this file");
	} 
}
 
}

How large are the numbers supposed to be?
To open file in append mode You use new FileWriter("fil eName", true);

[shana07]

How large are the numbers supposed to be?
To open file in append mode You use new FileWriter("fil eName", true);

Numbers between 1,000,000 - 100,000,000
Able for me to get those numbers?

[shana07]

This is the result :

0: 9896506
1: 9895847
2: 9897647
3: 9899801
4: 9904495
5: 9902275
6: 9900764
7: 9900471
8: 9901033
9: 9901161
10: 0
11: 0
12: 0
13: 0
14: 0
15: 0
16: 0
17: 0
18: 0
19: 0
20: 0
21: 0
22: 0
23: 0
24: 0
25: 0
26: 0
27: 0
28: 0
29: 0
30: 0
31: 0
32: 0
33: 0
34: 0
35: 0
36: 0
37: 0
38: 0
39: 0

[r035198x]

Numbers between 1,000,000 - 100,000,000
Able for me to get those numbers?

Yes you can use

 
final int million = 1000000;
final int hundredMillion = 100000000;
int[] ndigits = new int[40];
for (int i = 0; i < 40; i++) {
 int num = (int)(Math.random() * hundredMillion);
 if(million < 1000000) {
  num = num + million;
 }
 ndigits[i] = num;
}

Do you want the numbers to be unique?

[shana07]

Yes you can use

 
final int million = 1000000;
final int hundredMillion = 100000000;
int[] ndigits = new int[40];
for (int i = 0; i < 40; i++) {
 int num = (int)(Math.random() * hundredMillion);
 if(million < 1000000) {
  num = num + million;
 }
 ndigits[i] = num;
}

Do you want the numbers to be unique?

Yeah it works. TQ.
So we have to multiply the random numbers with max number to get between those range...
You mean the number won't be the same?
Yes please teach me that too...

[r035198x]

Yeah it works. TQ.
So we have to multiply the random numbers with max number to get between those range...
You mean the number won't be the same?
Yes please teach me that too...

What I meant to ask was, do you want each of the 40 random numbers to be different from each other (as in no duplicates).

[shana07]

What I meant to ask was, do you want each of the 40 random numbers to be different from each other (as in no duplicates).

Yes, please teach me :)

[r035198x]

Yes, please teach me :)

What do you think can be done to achieve that?

[shana07]

What do you think can be done to achieve that?

We have to compare between a & b
if a == b
then generate again random numbers? ;)

[r035198x]

We have to compare between a & b
if a == b
then generate again random numbers? ;)

Which a and b? Remember we are storing the ones we have already generated in the array called ndigits.

[shana07]

Which a and b? Remember we are storing the ones we have already generated in the array called ndigits.

I thought I can suprise you by doing this simple logic myself first. But I need to refer to you still...
Okay what I can think is something like:
ex:
if (ndigits[1] == ndigits[0])
{
num=regenerate random number;
ndigits [1];
}
How is that?

[shana07]

I thought I can suprise you by doing this simple logic myself first. But I need to refer to you still...
Okay what I can think is something like:
ex:
if (ndigits[1] == ndigits[0])
{
num=regenerate random number;
ndigits [1];
}
How is that?

I got it....Yeah :) Thanks to you.

 for (int i = 0; i < 40; i++) 
   {
               int num = (int)(Math.random() * hundredMillion);
               if(million < 1000000) 
               {
                num = num + million;
               }
               ndigits[i] = num;
                              
                if (ndigits[i] == ndigits[i-0]) 
                {       
                   num = (int)(Math.random() * hundredMillion);
                   if(million < 1000000) 
                   {
                    num = num + million;
                   }
                   ndigits[i] = num;                  
                }          
   }

[shana07]

I got it....Yeah :) Thanks to you.

 for (int i = 0; i < 40; i++) 
   {
               int num = (int)(Math.random() * hundredMillion);
               if(million < 1000000) 
               {
                num = num + million;
               }
               ndigits[i] = num;
                              
                if (ndigits[i] == ndigits[i-0]) 
                {       
                   num = (int)(Math.random() * hundredMillion);
                   if(million < 1000000) 
                   {
                    num = num + million;
                   }
                   ndigits[i] = num;                  
                }          
   }

Opss...I've checked...nope. ..still not unique number :P, please help to check it

[r035198x]

I got it....Yeah :) Thanks to you.

 for (int i = 0; i < 40; i++) 
{
int num = (int)(Math.random() * hundredMillion);
if(million < 1000000) 
{
num = num + million;
}
ndigits[i] = num;
 
if (ndigits[i] == ndigits[i-0]) 
{ 
num = (int)(Math.random() * hundredMillion);
if(million < 1000000) 
{
num = num + million;
}
ndigits[i] = num; 
} 
}

if (ndigits[i] == ndigits[i-0]) is just the same as
if (ndigits[i] == ndigits[i]) which will always be true and so does not help you at all. What you need is a separate method called, say, isInArray which looks like this

 
public static boolean isInArray(int[] array, int num) {
//do some logic here to determine if 
//the int num is in the array called array
 
}