I want num to be a random number between 0 and .99999, and it has to print and write 10 of them.
hm.
{
double num = Math.random();
publicvoid writeData()
{
FileWriter f1 =new FileWriter("random.txt");
if (num >= 0 || num <=.99999)
{
for (int i=1; i<10; i++)
{
f1.write(num);
System.out.println(num);
}
}
}
> FileProcessing.java:20: cannot find symbol
> symbol : method write(double)
> location: class java.io.FileWriter
> f1.write(num);
>^
> error
> Press any key to continue . . .
It's telling you exactly what's wrong. At line 20 of FileProcessing.java, you're trying to call a method in a FileWriter that doesn't exist. FileWriter has no write(double) method.
i'm getting a cannot find symbol when i used that line. I'm created it when i use this line, aren't i?
file = new PrintWriter(new FileWriter("random.txt"));
FileProcessing.java:15: cannot find symbol
symbol : variable file
location: class FileProcessing
file = new PrintWriter(new FileWriter("random.txt"));
^
added the throws, hows it look?
double num = Math.random();
public void writeData() throws IOException
{
PrintWriter pW = new PrintWriter(new FileWriter("random.txt"));
if (num >= 0 || num <=.99999)
{
for (int i=1; i<10; i++)
{
pW.print(num);
System.out.println(num);
}
}
}
> yeah i do, isn't the for loop doing that?
The for loop is taking the random number you made and printing it ten times. You need to set num to a new random number in the loop.
> i guess i
> should change the or operator to an AND?
You could, but [url=http://java.sun.com/j2se/1.5.0/docs/api/java/lang/Math.html#random()]Math.random()[/url] will always return a number between 0 (inclusive) and 1 (exclusive).
0.3729156571687533
1.3729156571687533
2.372915657168753
3.372915657168753
4.372915657168753
5.372915657168753
6.372915657168753
7.372915657168753
8.372915657168754
thats with num++..
this is with num = Math.random()
0.6723590899096302
0.248535991672175
0.6762380773686422
0.5740173978763413
0.7918507097449482
0.9116662958972523
0.4572605335927178
0.4043243994741199
0.8040561948675174
#2 for the win :)
public void readData() throws IOException
{
FileReader fr = new FileReader("random.txt");
BufferedReader br = new BufferedReader(fr);
String inRecord, number;
while ((inRecord = br.readLine()) != null)
{
StringTokenizer tokenizer = new StringTokenizer(inRecord);
number = tokenizer.nextToken();
System.out.println(number);
}
}
Shouldn't this print? i do realize StringTokenizer it used to print letters or whatever after a delimeter, but can't it work in this situation?
Not sure why it's not writing to the file.. it creates it. but makes it empty
double num = Math.random();
public void writeData() throws IOException
{
PrintWriter pW = new PrintWriter(new FileWriter("random.txt"));
if (num >= 0 && num <=.99999)
{
for (int i=1; i<10; i++)
{
pW.print(num);
num = Math.random();
}
}
}
public void readData() throws IOException
{
FileReader fr = new FileReader("random.txt");
BufferedReader br = new BufferedReader(fr);
String inRecord, number;
while ((inRecord = br.readLine()) != null)
{
StringTokenizer tokenizer = new StringTokenizer(inRecord);
number = tokenizer.nextToken();
System.out.println(number);
}
}
What is in random.txt? Have you looked in the file to verify this?
Are you sure no exception is being thrown?
This demo runs your read method, and it works for me.
import java.io.*;
import java.util.*;
public class IOExample {
public static void main(String[] args) throws IOException {
String filename = "random.txt";
write(filename);
read(filename);
}
public static void write(String filename) throws IOException {
PrintWriter out = new PrintWriter(filename);
try {
for(int i = 0; i < 10; ++i)
out.println(i);
} finally {
out.close();
}
}
public static void read(String filename) throws IOException {
FileReader fr = new FileReader(filename);
BufferedReader br = new BufferedReader(fr);
String inRecord, number;
while ((inRecord = br.readLine()) != null) {
StringTokenizer tokenizer = new StringTokenizer(inRecord);
number = tokenizer.nextToken();
System.out.println(number);
}
}
}
> While you're at it, you should close the stream in
> your input method.
> Forgetting to close it isn't as bad as fir output
> streams, but it's good hygiene.
That i did, Thank you sir :)
public void writeData() throws IOException
{
PrintWriter pW = new PrintWriter("random.txt");
if (num >= 0 && num <=.99999)
{
for (int i=1; i<10; i++)
{
pW.print(num +" \n ");
num = Math.random();
}
}
pW.close();
}
> >The test for num doesn't make sense? The if you
> mean? It works?.. lol.
>
> Well, I suppose it works *nearly* all the time...
Yeah but i don't think the assignment really focuses on the numbers, it's mostly just writing.. reading files.
By the way, what should i use for deleting a file?
In this case. I write to a file, read it and display it, and now i have to delete it.
Couple of points. Didn't you want 10 numbers? Your code will generate 9. Secondly, you if statement is totally pointless as others have pointed out. Yes it works becuase it will always be true. Try this code instead.
public void writeData() throws IOException {
int num = -1;
PrintWriter pW = new PrintWriter("random.txt");
for (int i = 0; i < 10; i++) {
num = Math.random();
pW.print(num +" \n ");
}
pW.close();
}
Thanks flounder. I'm trying to delete the file now but it gives me this.
try {
pW.delete();
System.out.println("Successfully deleted");
}
catch (SecurityException e)
{
System.out.println("Caught security exception trying to delete file");
}
Test.java:36: cannot find symbol
symbol : method delete()
location: class java.io.PrintWriter
pW.delete();
^
.
> ava:36: cannot find symbol
> symbol : method delete()
> location: class java.io.PrintWriter
> pW.delete();
>^
http://java.sun.com/javase/6/docs/api/java/io/PrintWriter.html
I don't know why you'd try to use a delete() method of PrintWriter, since no such method exists. Did you mean to call delete() on a File reference instead?
~
0.5452577623853672
0.4867849123685448
Exception in thread "main" java.util.NoSuchElementException
at java.util.StringTokenizer.nextToken(StringTokenizer.java:332)
at Test.main(Test.java:32)
Press any key to continue . . .
Doesn't print out the print statement.. and doesn't delete.
try {
File f = new File("random.txt");
f.delete();
System.out.println("Successfully deleted");
}
catch (SecurityException e)
{
System.out.println("Caught security exception trying to delete file");
}
Oh man, sorry,
heres the code, but when i take off the tokenizer stuff, it says number hasn't been instantiated, if i instantiate it with a value then it prints out the value on each.
FileReader fr = new FileReader("random.txt");
BufferedReader br = new BufferedReader(fr);
String inRecord, number;
while ((inRecord = br.readLine()) != null)
{
StringTokenizer tokenizer = new StringTokenizer(inRecord);
number = tokenizer.nextToken();
System.out.println(number);
}
> yeah but i'm getting the tokenizer error. :(
As mentioned previously, it's because you're calling nextElement() on a StringTokenizer that has no more elements. I recommend you have a look at the API javadocs for StringTokenizer and see if you can find a method that will ask the StringTokenizer object if it has any more elements. Only if it answers affirmatively should you call the nextElement() method.
~
