Lambda Expressions

A lambda expression is a concise anonymous function with syntax (params) -> body that implements a functional interface's single abstract method, replacing verbose anonymous inner classes.

A lambda has no type of its own: the compiler determines its functional interface type from the target context (variable, parameter, return, or cast), and ambiguity arises when two overloaded parameters share the same lambda shape.

Lambdas capture value copies of local variables, so Java requires them to be effectively final to prevent stale-copy bugs. Use AtomicInteger or reduce/collect instead of mutable capture.

There is no behavioral difference: effectively final variables (never reassigned) and explicitly final variables (final keyword) are treated identically by the compiler for lambda capture.

Java lambdas capture the value of local variables (not the variable binding), so the reference is final but the referenced object can be mutated.