bits2array.html

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<TITLE>Converting Between a BitSet and a Byte Array
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  <h3>
    e364.  
    Converting Between a BitSet and a Byte Array</h3>

There are no default methods for converting a <code>BitSet</code> to and from
a byte array.  This example implements two methods to do the
conversion.  These methods make it possible to easily work with both
<code>BitSet</code> and <code>BigInteger</code> and take advantage of their
capabilities when needed.


<pre>
    // Returns a bitset containing the values in bytes.
    // The byte-ordering of bytes must be big-endian which means the most significant bit is in element 0.
    public static BitSet fromByteArray(byte[] bytes) {
        BitSet bits = new BitSet();
        for (int i=0; i&lt;bytes.length*8; i++) {
            if ((bytes[bytes.length-i/8-1]&amp;(1&lt;&lt;(i%8))) &gt; 0) {
                bits.set(i);
            }
        }
        return bits;
    }
    
    // Returns a byte array of at least length 1.
    // The most significant bit in the result is guaranteed not to be a 1
    // (since BitSet does not support sign extension).
    // The byte-ordering of the result is big-endian which means the most significant bit is in element 0.
    // The bit at index 0 of the bit set is assumed to be the least significant bit.
    public static byte[] toByteArray(BitSet bits) {
        byte[] bytes = new byte[bits.length()/8+1];
        for (int i=0; i&lt;bits.length(); i++) {
            if (bits.get(i)) {
                bytes[bytes.length-i/8-1] |= 1&lt;&lt;(i%8);
            }
        }
        return bytes;
    }
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            &nbsp;Related Examples
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e363. <a class="eglink" href="Bits.html?l=rel">
    Performing Bitwise Operations on a Bit Vector
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        See also: 
<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Arrays">
    Arrays
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Collections">
    Collections
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Dates">
    Dates
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    Hash Tables
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    Lists
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    Property Files
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sets">
    Sets
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Sorted%20Collections">
    Sorted Collections
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<a class="eglink" href="/egs/java.util/pkg.html?l=rel#Time">
    Time
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    Timers
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