Class InnerAssignmentCheck

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().

To configure the check:

 <module name="InnerAssignment"/>
 

Example:

 class MyClass {

   void foo() {
     int a, b;
     a = b = 5; // violation, assignment to each variable should be in a separate statement
     a = b += 5; // violation

     a = 5; // OK
     b = 5; // OK
     a = 5; b = 5; // OK

     double myDouble;
     double[] doubleArray = new double[] {myDouble = 4.5, 15.5}; // violation

     String nameOne;
     List<String> myList = new ArrayList<String>();
     myList.add(nameOne = "tom"); // violation
     for (int k = 0; k < 10; k = k + 2) { // OK
       // some code
     }

     boolean someVal;
     if (someVal = true) { // violation
       // some code
     }

     while (someVal = false) {} // violation

     InputStream is = new FileInputStream("textFile.txt");
     while ((b = is.read()) != -1) { // OK, this is a common idiom
       // some code
     }

   }

   boolean testMethod() {
     boolean val;
     return val = true; // violation
   }
 }
 

Parent is com.puppycrawl.tools.checkstyle.TreeWalker

Violation Message Keys:

• assignment.inner.avoid