Java Byte Array conversion Issue

Question

I have a string which contains a series of bits (like "01100011") and some Integers in a while loop. For example:

while (true) {
    int i = 100;
    String str = Input Series of bits

    // Convert i and str to byte array
}

Now I want a nice fastest way to convert string and int to byte array. Until now, what I have done is convert int to String and then apply the getBytes() method on both strings. However, it is little bit slow. Is there any other way to do that which is (may be) faster than that?

@dash1e, no relation. I just show an example. i and str are different. str is not i 's bit representation. — Arpssss
– Arpssss, Commented Apr 7, 2012 at 4:55
So you need two separate and fast function to convert intengers or bit string in byte array? — dash1e
– dash1e, Commented Apr 7, 2012 at 4:56

Visionary Software Solutions · Accepted Answer · 2012-04-07 05:41:56Z

7

You can use the Java ByteBuffer class!

Example

byte[] bytes = ByteBuffer.allocate(4).putInt(1000).array();

edited Apr 7, 2012 at 5:41

Visionary Software Solutions

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answered Apr 7, 2012 at 4:55

Kevin

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1 Comment

Arpssss Over a year ago

Is this available in java inbuilt packages ?

Keith Randall · Accepted Answer · 2012-04-07 04:59:11Z

2

Converting an int is easy (little endian):

byte[] a = new byte[4];
a[0] = (byte)i;
a[1] = (byte)(i >> 8);
a[2] = (byte)(i >> 16);
a[3] = (byte)(i >> 24);

Converting the string, first convert to integer with Integer.parseInt(s, 2), then do the above. Use Long if your bitstring may be up to 64 bits, and BigInteger if it will be even bigger than that.

answered Apr 7, 2012 at 4:59

Keith Randall

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Comments

dash1e · Accepted Answer · 2012-04-07 08:08:30Z

1

For int

public static final byte[] intToByteArray(int i) {
    return new byte[] {
            (byte)(i >>> 24),
            (byte)(i >>> 16),
            (byte)(i >>> 8),
            (byte)i};
}

For string

byte[] buf = intToByteArray(Integer.parseInt(str, 2))

edited Apr 7, 2012 at 8:08

answered Apr 7, 2012 at 5:00

dash1e

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2 Comments

Rushil Paul Over a year ago

The string can contain at most 32 bits (without leading zeros). And you need to put it in a byte array, so that's wrong

dash1e Over a year ago

Ok, you need to process 8 bit per 8 bit, or reuse intToByteArray.

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