How to convert hex string to float in Java?

Question

How to convert hexadecimal string to single precision floating point in Java?

For example, how to implement:

float f = HexStringToFloat("BF800000"); // f should now contain -1.0

I ask this because I have tried:

float f = (float)(-1.0);
String s = String.format("%08x", Float.floatToRawIntBits(f));
f = Float.intBitsToFloat(Integer.valueOf(s,16).intValue());

But I get the following exception:

java.lang.NumberFormatException: For input string: "bf800000"

John Meagher · Accepted Answer · 2009-07-02 00:26:48Z

26

public class Test {
  public static void main (String[] args) {

        String myString = "BF800000";
        Long i = Long.parseLong(myString, 16);
        Float f = Float.intBitsToFloat(i.intValue());
        System.out.println(f);
        System.out.println(Integer.toHexString(Float.floatToIntBits(f)));
  }
}

edited Jul 2, 2009 at 0:26

answered Jul 2, 2009 at 0:04

John Meagher

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9 Comments

apalopohapa Over a year ago

I get: java.lang.NumberFormatException: For input string: "BF800000"

apalopohapa Over a year ago

When testing: Float.intBitsToFloat(Integer.valueOf("BF800000",16).intValue()); I get the exception: java.lang.NumberFormatException: For input string: "BF800000"

John Meagher Over a year ago

It's overflowing an int. Switching it to Long.valueOf(myString, 16) doesn't throw the exception, but results in -1.0 instead of 10.0. Are you sure 10.0 is the correct result?

Victor Over a year ago

that number is too big maybe? try using Long instead of integer.

Victor Over a year ago

i'm with john here, i'm getting -1.0 not 10.0

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Tano · Accepted Answer · 2009-07-02 00:05:37Z

2

You need to convert the hex value to an int (left as an exercise) and then use Float.intBitsToFloat(int)

answered Jul 2, 2009 at 0:05

Tano

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