This is valid code as per compiler:

BiPredicate<String, String> bp = String::equalsIgnoreCase;

But if I make my own BiPredicate, it fails to compile.. why?

 private void run() {
    BiPredicate<String, String> bp = String::equalsIgnoreCase; // compiles!
    BiPredicate<String, String> bp2 = MyKlazz::m1; // does not compile!
}

static final class MyKlazz<T, U> {
    private T t;
    MyKlazz(T t){
        this.t = t;
    }
    public boolean m1(U u){
        System.out.println("in m1.. t: " + this.t + ", u: " + u);
        return true; // dummy 
    }
}