InnerAssignment.md

Pattern: Use of inner assignment

Issue: -

Description

Checks for assignments in subexpressions, such as in String s = Integer.toString(i = 2);.

Rationale: With the exception of for iterators and assignment in while idiom, all assignments should occur in their own top-level statement to increase readability. With inner assignments like the one given above, it is difficult to see all places where a variable is set.

Note: check allows usage of the popular assignment in while idiom:

String line;
while ((line = bufferedReader.readLine()) != null) {
   // process the line
}

Assignment inside a condition is not a problem here, as the assignment is surrounded by an extra pair of parentheses. The comparison is != null and there is no chance that intention was to write line == reader.readLine().

Examples

To configure the check:

<module name="InnerAssignment"/>

To configure the check for only =, +=, and -= operators:

<module name="InnerAssignment">
    <property name="tokens" value="ASSIGN,PLUS_ASSIGN,MINUS_ASSIGN"/>
</module>

Further Reading

• checkstyle - InnerAssignment