[FIXED] Java 11 Predicate lambda expression generic type ClassCastException

Issue

I have problem on java 11 predicate lambda expression generic type , when I write predicate as lambda expression is not returning exactly generic parameter ,and ClassCastException occurs , code seen below

Explaination When we write lambda expression , Generic Parameter method getGenericInterfaces()[0] -> ClassCastException occurs this line because there no generic parameter seen when I debugged code , seen as just Condition not Condition<<Integer>>, anyway when we define predicate as seen below (working case) , its working

Working Case

Condition<Integer> oddValueCondition = new Condition<Integer>() {
    @Override
    public boolean test(Integer integer) {
        return integer % 2 == 0;
    }
};

Not Working Case

Condition<Integer> oddValueCondition = integer -> integer % 2 == 0;

interface definition

@FunctionalInterface
public interface Condition<T> extends Predicate<T> {
    default Class<T> getParameterType() {
        ParameterizedType parameterizedType = (ParameterizedType) this.getClass().getGenericInterfaces()[0];
        Type[] typeArguments = parameterizedType.getActualTypeArguments();
        Class<T> type = (Class<T>) typeArguments[0];
        return type;
    }
}

Test

oddValueCondition.getParameterType();

So what do you think problem is , when write lambda expression ?

And also I created issue on the github OpenJDK

if they says TypeReference Hack is not work on anonymous class and lambda expression , I will accept answer

Solution

Lambda expressions and anonymous inner classes don't compile to the same byte-code.

The TypeReference hack doesn't work with lambda as the type information is not available through this API. And by the way, this has been like this since Java 1.8.

Answered By - Sleiman Jneidi
Answer Checked By - Mildred Charles (JavaFixing Admin)