Wrong Output (Java Program)

[poupas]

hi guys... this is my program and i dont know what is wrong:S
The problem is in the main i guess..Can you guys help me please? thanks for everything

public class Xiu {
public static void main (String []args)
{
int max = 50;
System.out.print(enigma(max)+ " ");
}
public static boolean[] enigma(int max) {
boolean[] res = new boolean[max+1];
for (int i = 0; i < 2; i++) res[i] = false;
for (int i = 2; i < res.length; i++) res[i] = true;
for (int i = 2; i < res.length; i++)
if (res[i])
for (int j = i; i * j < res.length; j++)
res[i * j] = false;
return res;
}
}

[Iron Lion]

What are you expecting it to do? What is it doing differently to that?

Also, it would help if you used the [code] tags to format your code.

[poupas]

i dont know to use code tags for now :S What i want to do is put the method enigma working :S It should give false in 0 and 1 index and then false in i x i index (ex: 2 x 2, 3 x 3, ...) until max + 1. The rest index are true.. I know the method is right, the problem is how to put it working in the main :S

[m00nchile]

You have to iterate through every element and print it out. What you're probably getting as output is something like this:
@245ae567b76
That's the memory location of the array.

[poupas]

yes moonchile im getting that output...i put a for () but still not working

public class Xiu {
public static void main (String []args)
{
int max = 50;
for (int i = 0; i < max+1; i++)
System.out.print(enigma(max)+ " ");
}
public static boolean[] enigma(int max) {
boolean[] res = new boolean[max+1];
for (int i = 0; i < 2; i++) res[i] = false;
for (int i = 2; i < res.length; i++) res[i] = true;
for (int i = 2; i < res.length; i++)
if (res[i])
for (int j = i; i * j < res.length; j++)
res[i * j] = false;
return res;
}
}

[Fubarable]

i dont know to use code tags for now...

Many of us here will wait for you to learn. To use them, highlight your pasted code (please be sure that it is already formatted when you paste it into the forum; the code tags don't magically format unformatted code) and then press the code button, and your code will have tags.

Another way to do this is to manually place the tags into your code by placing the tag [cod&#101;] above your pasted code and the tag [/cod&#101;] below your pasted code like so:

[code]
  // your code goes here
  // notice how the top and bottom tags are different
[/code]

[Fubarable]

I've added tags to your post above, but the code in your post wasn't formatted to begin with, and tags won't magically make unformatted code formatted. Also, you need to tell us more, since "it still doesn't work" doesn't tell us much about how it's currently not working.

[poupas]

ok guys i got it to work.. Thanks for everything.

The progrmam should be like this:


public class Xiu {
public static void main (String []args)
{
int max = 50;
for (int i = 0;i< max+1; ++i)
{
System.out.println ((enigma(max)[i]));
}
}
public static boolean[] enigma(int max)
{
boolean[] res = new boolean[max+1];
for (int i = 0; i < 2; i++) res[i] = false;
for (int i = 2; i < res.length; i++) res[i] = true;
for (int i = 2; i < res.length; i++)
if (res[i])
for (int j = i; i * j < res.length; j++)
res[i * j] = false;
return res;
}
}

OutPut: Prime Numbers (True) until max;

[m00nchile]

ok guys i got it to work.. Thanks for everything.

The progrmam should be like this:


public class Xiu {
public static void main (String []args)
{
int max = 50;
for (int i = 0;i< max+1; ++i)
{
System.out.println ((enigma(max)[i]));
}
}
public static boolean[] enigma(int max)
{
boolean[] res = new boolean[max+1];
for (int i = 0; i < 2; i++) res[i] = false;
for (int i = 2; i < res.length; i++) res[i] = true;
for (int i = 2; i < res.length; i++)
if (res[i])
for (int j = i; i * j < res.length; j++)
res[i * j] = false;
return res;
}
}

OutPut: Prime Numbers (True) until max;

Why don't you save the result array of the enigma method? The way you've written your method, you call the enigma method max+1 times, which is horribly inefficient.

[JosAH]

I've added tags to your post above, but the code in your post wasn't formatted to begin with, and tags won't magically make unformatted code formatted. Also, you need to tell us more, since "it still doesn't work" doesn't tell us much about how it's currently not working.

The OP is trying to implement a Sieve of Erastosthenes; that works, just the printing of the boolean array fails. hint for the OP: use Arrays.toString(res) and print that.

kind regards,

Jos

[poupas]

Why don't you save the result array of the enigma method? The way you've written your method, you call the enigma method max+1 times, which is horribly inefficient.

I cant change my method because the exercise im doing told me that i must not change the method :X sry for my english xP

[JosAH]

I cant change my method because the exercise im doing told me that i must not change the method :X sry for my english xP

Still then ... why don't you simply do this:

boolean[] result= enigma(max); // calculate the result once
for (int i= 0; i < result.length; i++)
   System.out.println(result[i]);

kind regards,

Jos

[poupas]

Still then ... why don't you simply do this:

boolean[] result= enigma(max); // calculate the result once
for (int i= 0; i < result.length; i++)
   System.out.println(result[i]);

oh yeah, you re right ^^
much easier :X Thanks ^^