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POWhy doesn't Java have compound assignment versions of the conditional-and and conditional-or operators? (&&=, ||=)
 

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  1. POWhy doesn't Java have compound assignment versions of the conditional-and and conditional-or operators? (&&=, ||=)
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    <p>So for binary operators on booleans, Java has <code>&amp;</code>, <code>|</code>, <code>^</code>, <code>&amp;&amp;</code> and <code>||</code>.</p> <p>Let's summarize what they do briefly here:</p> <ul> <li><a href="http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.22.2" rel="noreferrer">JLS 15.22.2 Boolean Logical Operators &amp;, ^, and |</a></li> <li><a href="http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.23" rel="noreferrer">JLS 15.23 Conditional-And Operator &amp;&amp;</a> </li> <li><a href="http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.24" rel="noreferrer">JLS 15.24 Conditional-Or Operator ||</a></li> </ul> <blockquote> <p>For <code>&amp;</code>, the result value is <code>true</code> if both operand values are <code>true</code>; otherwise, the result is <code>false</code>.</p> <p>For <code>|</code>, the result value is <code>false</code> if both operand values are <code>false</code>; otherwise, the result is <code>true</code>.</p> <p>For <code>^</code>, the result value is <code>true</code> if the operand values are different; otherwise, the result is <code>false</code>.</p> <p>The <code>&amp;&amp;</code> operator is like <code>&amp;</code> but evaluates its right-hand operand only if the value of its left-hand operand is <code>true</code>.</p> <p>The <code>||</code> operator is like <code>|</code>, but evaluates its right-hand operand only if the value of its left-hand operand is <code>false</code>.</p> </blockquote> <p>Now, among all 5, 3 of those have compound assignment versions, namely <code>|=</code>, <code>&amp;=</code> and <code>^=</code>. So my question is obvious: why doesn't Java provide <code>&amp;&amp;=</code> and <code>||=</code> as well? I find that I need those more than I need <code>&amp;=</code> and <code>|=</code>.</p> <p>And I don't think that "because it's too long" is a good answer, because Java has <code>&gt;&gt;&gt;=</code>. There must be a better reason for this omission.</p> <hr> <p>From <a href="http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.26" rel="noreferrer">15.26 Assignment Operators</a>:</p> <blockquote> <p>There are 12 assignment operators; [...] <code>= *= /= %= += -= &lt;&lt;= &gt;&gt;= &gt;&gt;&gt;= &amp;= ^= |=</code></p> </blockquote> <hr> <p>A comment was made that if <code>&amp;&amp;=</code> and <code>||=</code> were implemented, then it would be the only operators that do not evaluate the right hand side first. I believe this notion that a compound assignment operator evaluates the right hand side first is a mistake.</p> <p>From <a href="http://java.sun.com/docs/books/jls/third_edition/html/expressions.html#15.26.2" rel="noreferrer">15.26.2 Compound Assignment Operators</a>:</p> <blockquote> <p>A compound assignment expression of the form <code>E1 op= E2</code> is equivalent to <code>E1 = (T)((E1) op (E2))</code>, where <code>T</code> is the type of <code>E1</code>, except that <code>E1</code> is evaluated only once. </p> </blockquote> <p>As proof, the following snippet throws a <code>NullPointerException</code>, not an <code>ArrayIndexOutOfBoundsException</code>.</p> <pre><code> int[] a = null; int[] b = {}; a[0] += b[-1]; </code></pre>
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    1. COI go for the second, no one cares :P also, all these question about 'why feature x is not in language y?' should be asked to the language's designers, not to us :P
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    2. COWhat does &= mean ? Some one please can tell me ?
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    3. CO@Aaron: a = a & b. It's written in the question
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