Lambdas

Question 1

What is the method signature of Predicate

Answer 1

public boolean test(T t)

It only has one abstract method.

Question 2

Can a functional interface have other default or static methods?

Answer 2

Yes, but it must also have exactly one abstract method.

Question 3

Is the following a valid lambda expression?

foo(newArrayList( ), ArrayList a1 -> a1.isEmpty ( ) );

Answer 3

No.

The parameter list should be in parenthesis:

foo(newArrayList( ), (List a1) -> a1.isEmpty( ) );

Question 4

What syntax is needed to use the return keyword in a lambda expression?

Answer 4

Curly braces.

ex.: foo(new ArrayList( ), al -> { return al.size( ) == 0; } );

Question 5

Does a lambda expression create a new scope for variables?

Answer 5

No.

You may not reuse variable names already defined as new variables in a lambda expression argument list.

Question 6

When can you omit curly braces in a lambda expression?

Answer 6

When all the method does is return the value of an expression.

Question 7

What is the only method of the java.util.function.Predicate interface?

Answer 7

test ( )

It returns a boolean.