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    <p>I'm going to be more explicit here because I think bitwise masks are a great tool that should be in any devs belt. I'm going to try to expand on the answers above. First, an example of using an integer to maintain state flags (common usage):</p> <pre><code>// These are my masks private static final int MASK_DID_HOMEWORK = 0x0001; private static final int MASK_ATE_DINNER = 0x0002; private static final int MASK_SLEPT_WELL = 0x0004; // This is my current state private int m_nCurState; </code></pre> <p>To <strong><em>set</em></strong> my state, I use the bitwise OR operator:</p> <pre><code>// Set state for'ate dinner' and 'slept well' to 'on' m_nCurState = m_nCurState | (MASK_ATE_DINNER | MASK_SLEPT_WELL); </code></pre> <p>Notice how I 'or' my current state in with the states that I want to turn 'on'. Who knows what my current state is and I don't want to blow it away. </p> <p>To <strong><em>unset</em></strong> my state, I use the bitwise AND operator with the complement operator:</p> <pre><code>// Turn off the 'ate dinner' flag m_nCurState = (m_nCurState &amp; ~MASK_ATE_DINNER); </code></pre> <p>To <strong><em>check</em></strong> my current state, I use the AND operator:</p> <pre><code>// Check if I did my homework if (0 != (m_nCurState &amp; MASK_DID_HOMEWORK)) { // yep } else { // nope... } </code></pre> <p>Why do I think this is interesting? Say I'm designing an interface that sets my state. I could write a method that accepts three booleans:</p> <pre><code>void setState( boolean bDidHomework, boolean bAteDinner, boolean bSleptWell); </code></pre> <p>Or, I could use a single number to represent all three states and pass a single value:</p> <pre><code>void setState( int nStateBits); </code></pre> <p>If you choose the second pattern you'll be very happy when decide to add another state - you won't have to break existing impls of your interface.</p> <p>My two cents. Thanks.</p>
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    1. POWhen to use Bitwise Operators during webdevelopment?
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    1. COA very helpful answer! deserves to be on top, for sure.
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    2. COPersonally, I hate this "pattern" with a vengeance. It's very close to code obfuscation.
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      1. USMichael Borgwardt
    3. COThough you are welcome to your opinion, I maintain that using bit fields to store state can be clean, concise and in some cases optimal. If it's the syntax that makes you uncomfortable then package the operations in problem specific convenience methods and avoid exposing the underlying implementation to your caller. As for code obfuscation, does a "pattern" exist that can't be obfuscated by an inexperienced developer?
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