I am trying to learn Java8 and have tried following example.
I am getting a compilation error for this code. Can you please help me to resolve this issue.
public class Lambdas {
public static void main(String[] args) {
System.out.println("Result Of Comparision" + () -> Integer.compare("First".length(), "Second".length()));
}
}
a lambda expression must have a target type that is a functional interface.
A lambda expression is compatible in an assignment context, invocation context, or casting context with a target type T if T is a functional interface type (§9.8) and the expression is congruent with the function type of the ground target type derived from T.
you can make your code compile by cast lambda expression to a special functional interface. e.g: IntSupplier.
class Lambdas {
public static void main(String[] args) {
System.out.println("Result Of Comparision"
+ (IntSupplier)() -> Integer.compare("First".length(), "Second".length()));
}
}
But then print lambda itself not the result you expected. so you need call the functional interface method to get the result.
class Lambdas {
public static void main(String[] args) {
System.out.println("Result Of Comparision"
+ ((IntSupplier)() -> Integer.compare("First".length(), "Second".length()))
.getAsInt());
}
}
@FunctionalInterface". Everywhere you write the second in your answer you should have the first instead.
@FunctionalInterface as functional interface. I will fix it.println needs a value to be print. You tried to add a String value to a function, and that is nonsense. A function have no value, a function is a...function, only a function call may produce a value.
toString() implementation returning an unspecified, most likely meaningless string. Perhaps that’s what you meant. The lambda expression itself has no value. In the current Java version, it doesn’t even have a type.String has an unspecified, meaningless result.