Java InputStream float value too big

Question

I am struggling how to read float value from inputStream. I tried before with BigDecimal, and it was not possible to get the correct number

Problem: im expecting V ~0.00 - 1.50, Later up to 55.00

While V = ~0.00, it prints 6.336931E-10, V = ~1.05 - 2.53483E-9

Java code:

DataInputStream inputStream = null;
 try {
 inputStream = new DataInputStream(btSocket.getInputStream());
 
 float f = inputStream.readFloat();
 System.out.println(f);
 } catch (IOException e) {
 e.printStackTrace();
 }

To visualize sent values:

example value

• Holger: What exactly is the purpose of inputStream.skip(inputStream.available())?
• Doublementi: It doesn't change anything, I can remove it and the value won't change
• Holger: "It doesn't change anything" does not explain why it’s there. That’s not how programming works. Don’t put random purposeless statements into your code. Besides that, any two-sided communication works by both sides having to agree about the format of the communication.
• chux: "V ~0.00 - 1.50, .... V = ~1.05 - 2.53483E-9" --> Is that really the right numbers: 1.50 and 1.05? IAC, more useful to print the exact output seen.

Answer 1

To read float values with DataInput, they need to be written in a compatible format, which is essentially a 32-bit IEEE 754 float.

Your Arduino code appears to be writing them as new-line separated decimal strings.

Those won't work together.

If you want to modify your Java to read text, something like this should work:

try (var is = btSocket.getInputStream();
 var r = new InputStreamReader(is, StandardCharsets.US_ASCII);
 var lines = new BufferedReader(r)) {
 while (true) {
 String line = lines.readLine();
 if (line == null) break;
 float f = Float.parseFloat(line);
 System.out.println(f);
 }
}