Java lambda - for loop counter is not effectively final

Question

Given this situation where a lambda is inside a for loop I would expect the counter i to be effectively final.

The compiler complains that i is not effectively final

Answer 1

From the Java Language Specification

The scope of a local variable declared in the ForInit part of a basic for statement (§14.14.1) includes all of the following:

• Its own initializer
• Any further declarators to the right in the ForInit part of the for statement
• The Expression and ForUpdate parts of the for statement
• The contained Statement

And about effectively final

A local variable or a method, constructor, lambda, or exception parameter is effectively final if it is not declared final but it never occurs as the left hand operand of an assignment operator (§15.26) or as the operand of a prefix or postfix increment or decrement operator

Your i variable occurs as the operand of postfix increment operator

i++

It is therefore not effectively final and can not be captured by the lambda.