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Programmers frequently make errors regarding the precedence of operators because of the unintuitive low-precedence levels of {{&}}, {{\|}}, {{\^}}, {{<<}}, and {{>>}}. Avoid mistakes regarding precedence through the suitable use of parentheses. This also improves code readability, unless taken to excess. The precedence of operations by the order of the subclauses are defined in the Java Tutorials \[[Tutorials 2008|AA. References#Tutorials 08]\]. |
Although it advises against depending on parentheses for specifying evaluation order, guideline "EXP08-J. Do not write more than once to the same variable within an expression" applies only to expressions that contain side effects.
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The intent of the expression in this noncompliant code example is to add the variable OFFSET to the result of the bitwise logical AND & between x and MASK.
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public static final int MASK = 1337;
public static final int OFFSET = -1337;
public static int computeCode(int x) {
return x & MASK + OFFSET;
}
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This expression gets evaluated, as shown belowfollows, resulting in the value 0.
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Related Guidelines
C Coding Standard: "EXP00-C. Use parentheses for precedence of operation"
C++ Secure Coding Standard: "EXP00-CPP. Use parentheses for precedence of operation"
Bibliography
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="ad3fa120ba5be76b-44202917-43754916-aaaa893e-c670ef0084a457dfee02333e"><ac:plain-text-body><![CDATA[ | [[ESA 2005 | AA. References#ESA 05]] | Rule 65: Use parentheses to explicitly indicate the order of execution of numerical operators | ]]></ac:plain-text-body></ac:structured-macro> | |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="fd421374e7feb168-10f111ab-491e427e-8bae8d2a-f17fec23ee8098b7f7643938"><ac:plain-text-body><![CDATA[ | [[Tutorials 2008 | AA. References#Tutorials 08]] | [Expressions, Statements, and Blocks | http://java.sun.com/docs/books/tutorial/java/nutsandbolts/expressions.html] | ]]></ac:plain-text-body></ac:structured-macro> |
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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="99463cfd26425342-134dd92b-46744ffe-b337b6d3-92257616857156f23eff7227"><ac:plain-text-body><![CDATA[ | [[Rogue 2000 | AA. References#Rogue 2000]] | Rule 77: Clarify the order of operations with parentheses | ]]></ac:plain-text-body></ac:structured-macro> |
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