Lambda Expressions: Accessing Local Variables of the Enclosing Scope
Accessing Local Variables of the Enclosing Scope
import java.util.function.Consumer;
public class LambdaScopeTest {
public int x = 0;
class FirstLevel {
public int x = 1;
void methodInFirstLevel(int x) {
// The following statement causes the compiler to generate
// the error "local variables referenced from a lambda expression
// must be final or effectively final" in statement A:
//
// x = 99;
Consumer<Integer> myConsumer = (y) ->
{
System.out.println("x = " + x); // Statement A
System.out.println("y = " + y);
System.out.println("this.x = " + this.x);
System.out.println("LambdaScopeTest.this.x = " +
LambdaScopeTest.this.x);
};
myConsumer.accept(x);
}
}
public static void main(String... args) {
LambdaScopeTest st = new LambdaScopeTest();
LambdaScopeTest.FirstLevel fl = st.new FirstLevel();
fl.methodInFirstLevel(23);
}
} - Like local and anonymous classes, lambda expressions can capture variables; they have the same access to local variables of the enclosing scope.
- However, unlike local and anonymous classes, lambda expressions do not have any shadowing issues.
- Lambda expressions are lexically scoped. This means that they do not inherit any names from a supertype or introduce a new level of scoping. Declarations in a lambda expression are interpreted just as they are in the enclosing environment.
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Accessing Local Variables of the Enclosing Scope
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