如何将float转换为字节数组，反之亦然？

Question

I am trying to convert a float into a primitive byte[] and vice versa:

public byte[] floatToByteArray(final float value)
{
    return new byte[]
    {
        (byte) (value >> 56),
        (byte) (value >> 48),
        (byte) (value >> 40),
        (byte) (value >> 32),
        (byte) (value >> 24),
        (byte) (value >> 16),
        (byte) (value >> 8),
        (byte) (value)
    };
}

Oddly enough, when I try to shift the newly allocated byte[] back into a float , the result is nothing but rubbish.

However, it would appear as if the same algorithm works just fine when I use the primitive long data type as argument instead.

public byte[] longToByteArray(final long value)
{
    return new byte[]
    {
        (byte) (value >> 56),
        (byte) (value >> 48),
        (byte) (value >> 40),
        (byte) (value >> 32),
        (byte) (value >> 24),
        (byte) (value >> 16),
        (byte) (value >> 8),
        (byte) (value)
    };
}

Answer 1

Use these instead.

public static byte [] long2ByteArray (long value)
{
    return ByteBuffer.allocate(8).putLong(value).array();
}

public static byte [] float2ByteArray (float value)
{  
     return ByteBuffer.allocate(4).putFloat(value).array();
}

Answer 2

Just to add another useful one based on @shazin solution. Convert a float array into a byte array:

public static byte[] FloatArray2ByteArray(float[] values){
    ByteBuffer buffer = ByteBuffer.allocate(4 * values.length);

    for (float value : values){
        buffer.putFloat(value);
    }

    return buffer.array();
}

Answer 3

It wont work. Float.byteValue just truncates float value to 1 byte

  public byte byteValue() {
        return (byte)value;
    }

Besides, it's not clear what bytes you want. Is it IEEE 754 floating-point single-float bit layout? Then you can first convert it to int

int i =  Float.floatToIntBits(1.1f);   // see Float API, there are actually 2 options

then use shifts to break it into 4 bytes or 8 bytes like you did

Answer 4

Also based on Shazin solution, with additional specification on byte order:

ByteBuffer.allocate(4).order(ByteOrder.LITTLE_ENDIAN).putFloat(value).array();

or

ByteBuffer.allocate(4).order(ByteOrder.BIG_ENDIAN).putFloat(value).array();

Answer 5

I cant see easy-to-use methods. It works:

public static byte[] toByteArray(float value) {
    byte[] bytes = new byte[4];
    ByteBuffer.wrap(bytes).putFloat(value);
    return bytes;
}

public static float toFloat(byte[] bytes) {
    return ByteBuffer.wrap(bytes).getFloat();
}