Java 泛型类的问题?

Question

public static class A<R extends Throwable> {
        private final Function<Throwable, R> function;

        public A() {
            this.function = ex -> ex;
        }
    }

为什么会报 Bad return type in lambda expression 的错误？

Answer 1

把返回的ex强转成R类型的就行了

public static class A<R extends Throwable> {
    private final Function<Throwable, R> function;

    public A() {
        this.function = ex -> (R) ex;
    }
}