How to convert int/float etc into byte[]?

[RC]

For example

int i = 2;
char c = 'c';
float f = (float)3.45;
double d = 3.546;
String s = "Hello";

I want to write all these into a binary file.

In OutputStream, PrintStream classes
they have

write(int byte); and
write(byte[] buffer, int offset, int length);

My question is how do I convert those i,c,f,d,s into
byte[]?

Thank Q in advance!

 

[Patricia Shanahan]

For example

int i = 2;
char c = 'c';
float f = (float)3.45;
double d = 3.546;
String s = "Hello";

I want to write all these into a binary file.

In OutputStream, PrintStream classes
they have

write(int byte); and
write(byte[] buffer, int offset, int length);

You can do it either the easy way, or the hard way.

The easy way is to wrap your OutputStream in a DataOutputStream and use
its writeInt, writeChar, writeFloat etc.

My question is how do I convert those i,c,f,d,s into
byte[]?

That would be the hard way. Do you still want to know?

Patricia

 

[RC]

For example

int i = 2;
char c = 'c';
float f = (float)3.45;
double d = 3.546;
String s = "Hello";

I want to write all these into a binary file.

In OutputStream, PrintStream classes
they have

write(int byte); and
write(byte[] buffer, int offset, int length);

You can do it either the easy way, or the hard way.

The easy way is to wrap your OutputStream in a DataOutputStream and use
its writeInt, writeChar, writeFloat etc.

Thank Q, I'll try that.

I tried this

Float ff = Float.valueOf((float)3.2);
byte b = ff.byteValue();

outputStream.write(b);

Is this make sense?

It is not make too much sense to me, because how do I know the
size of byte array (b)?

My question is how do I convert those i,c,f,d,s into
byte[]?

That would be the hard way. Do you still want to know?

Patricia

 

[Roedy Green]

I want to write all these into a binary file.

there are a number of techniques.

1. DataOutputStream.
see http://mindprod.com/applet/fileio.html for sample code.

2. LEDataOutputStream (for little endian).
See http://mindprod.com/applet/fileio.html for sample code.

3. Nio. See http://mindprod.com/jgloss/nio.html

4. serialised objects.
see http://mindprod.com/jgloss/serialization.html

5. Double.doubleToLongBits.
see http://mindprod.com/jgloss/jgloss/floatingpoint.html

 

[Roedy Green]

Float ff = Float.valueOf((float)3.2);
byte b = ff.byteValue();

outputStream.write(b);

no. You will end up with 3.

 

[Roedy Green]

Float ff = Float.valueOf((float)3.2);
byte b = ff.byteValue();

For the tersest conversions see
http://mindprod.com/applet/converter.html

Unfortunately for you, even Java's tightest conversions from float to
byte will give you a byte, not the 32-bit IEEE bit representation of
the value.

 

[Ben Phillips]

The easy way is to wrap your OutputStream in a DataOutputStream and use
its writeInt, writeChar, writeFloat etc.

My question is how do I convert those i,c,f,d,s into
byte[]?

That would be the hard way. Do you still want to know?

That is not the hard way; it is the not-quite-as-easy way.
DataOutputStream wrapping ByteArrayOutputStream.