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    <p>You are assuming that 101 is three bits long. Java doesn't support variable length bit operations, it operates on a whole <code>int</code> of bits, so <code>~</code> will be the <code>not</code> of a 32 bit long "101".</p> <p>--- Edited after being asked "How can I fix this?" ---</p> <p>That's a really good question, but the answer is a mix of "you can't" and "you can achieve the same thing by different means".</p> <p>You can't fix the <code>~</code> operator, as it does what it does. It would sort of be like asking to fix <code>+</code> to only add the 1's place. Just not going to happen.</p> <p>You can achieve the desired operation, but you need a bit more "stuff" to get it going. First you must have <em>something</em> (another int) that specifies the <em>bits of interest</em>. This is typically called a <strong>bit mask</strong>.</p> <pre><code> int mask = 0x00000007; // just the last 3 bits. int masked_inverse = (~value) &amp; mask; </code></pre> <p>Note that what we did was really invert 32 bits, then zeroed out 29 of those bits; because, they were set to zero in the mask, which means "we don't care about them". This can also be imagined as leveraging the <code>&amp;</code> operator such that we say "if set and we care about it, set it".</p> <p>Now you will <em>still</em> have 32 bits, but only the lower 3 will be inverted. If you want a 3 bit data structure, then that's a different story. Java (and most languages) just don't support such things directly. So, you might be tempted to add another <em>type</em> to Java to support that. Java adds types via a <em>class</em> mechanism, but the built-in types are not changeable. This means you could write a class to represent a 3 bit data structure, but it will have to handle ints internally as 32 bit fields.</p> <p>Fortunately for you, someone has already done this. It is part of the standard Java library, and <a href="http://docs.oracle.com/javase/1.4.2/docs/api/java/util/BitSet.html">is called a <code>BitSet</code></a>. </p> <pre><code>BitSet threeBits = new BitSet(3); threeBits.set(2); // set bit index 2 threeBits.set(0); // set bit index 0 threeBits.flip(0,3); </code></pre> <p>However, such bit manipulations have a different feel to them due to the constraints of the Class / Object system in Java, which follows from defining classes as the <em>only way</em> to add new types in Java.</p>
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    1. COso how would i fix this
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      1. USJosh Sobel
    2. CO@JoshSobel I updated the answer. Some really short questions require long explanations, as they are just lucky enough to open up doors of new understanding. Good luck on your endeavor.
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    3. CObut how would i dynamically adjust the mask to fit the given number
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