PhoneNumber(String phoneNumber) {
    numberLength = 7;   // <== assignment to numberLength
    String currentNumber = phoneNumber.replaceAll(
        regularExpression, "");
    if (currentNumber.length() == numberLength)
        formattedPhoneNumber = currentNumber;
    else
        formattedPhoneNumber = null;
}

public class Foo {

    public void baz(int bar) {
        // While the next line is commented, bar is effectively final
        // and while it is uncommented, the assignment means it is not
        // effectively final.

        // bar = 2;
    }
}

final int variable = 123;

int variable = 123;
variable = 456;

int variable = 123;

final int number;
number = 23;

int number;
number = 34;

@FunctionalInterface
interface IFuncInt {
    int func(int num1, int num2);
    public String toString();
}

public class LambdaVarDemo {

    public static void main(String[] args){
        int i = 7;
        IFuncInt funcInt = (num1, num2) -> {
            i = num1 + num2;
            return i;
        };
    }
}

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;

        }
    }
}

String str = ""; //<-- not accesible from anonymous classes implementation
final String strFin = ""; //<-- accesible
button.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
         String ann = str; // <---- error, must be final (IDE's gives the hint);
         String ann = strFin; // <---- legal;
         String str = "legal statement on java 7,"
                +"Java 8 doesn't allow this, it thinks that I'm trying to use the str declared before the anonymous impl.";
         //we are forced to use another name than str
    }
);