CODEWITHSUNDEEP
javafloating-point
newQuesion
newQuesion

Reputation: 63

processing float in java

in java, i have an array of floats, some of them are negative numbers, like :

3.04, 9.02, -4.2, -3.21, 0.02, -0.34

I only want to get the float numbers higher than 2, so I used :

if(number > 2.0 ) print.. etc

but what i get is not only the numbers >2, also the negative numbers :

3.04, 9.02, -4.2, -3.21

what could be the problem ?

Upvotes: 0

Views: 670

Answers (3)

Gugussee
Gugussee

Reputation: 1713

This is too long for a comment but it should be pointed out that if you write:

if (number > 2.0)

then you probably shouldn't be working with floating-point numbers because you don't understand yet how they work.

There's a good Wikipedia page on floating point numbers:

http://en.wikipedia.org/wiki/Floating_point

Then I suggest reading the 80 pages long "What every computer scientist should know about floating-point numbers".

Basically: due to the limited precision of floating point numbers, comparison should typically always be done using an epsilon.

Things like: if (number > 2.0) are a big no-no.

Upvotes: -1

darioo
darioo

Reputation: 47183

Based on comments and question, assuming we have a file named numbers.txt with content:

3.04 
9.02 
-4.2 
-3.21 
0.02 
-0.34

this code should do the trick (I ommited exception handling for readibility):

float[] floats = new float[100];  // adjust as needed

String fileName = "numbers.txt";
File f = new File(fileName);
BufferedReader br = new BufferedReader(new FileReader(f));

String line = "";

int i = 0;

while( (line = br.readLine()) != null) {

    if(line == null || line.isEmpty()) continue;  // just in case there are empty lines in file
    floats[i] = Float.parseFloat(line);
    i++;
}

br.close();

for (float number : floats) {
    if (number > 2.0) {
        System.out.println(number);
    }
}

Output:

3.04
9.02

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1499770

It's hard to tell what the problem is without seeing code. Writing the obvious code from your description, it works fine:

public class Test {
    public static void main(String[] args) {
        float[] floats = { 3.04f, 9.02f, -4.2f, -3.21f, 0.02f, -0.34f };

        for (float number : floats) {
            if (number > 2.0) {
                System.out.println(number);
            }
        }
    }
}

Compare your code with mine - if you still can't get yours to work, please edit your question with your code.

Upvotes: 3

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