Javac defines this abstract class in Type:

public static abstract class Mapping {
        private String name;
        public Mapping(String name) {
            this.name = name;
        }
        public abstract Type apply(Type t);
        public String toString() {
            return name;
        }
    }

This abstract class is essentially treated as a functional interface:

            Mapping boxMap = new Mapping("boxMap") {
                @Override
                public Type apply(Type t) {
                    return types.boxedTypeOrType(t);
                }
            };


It would be better if this class was refactored to take advantage of lambda expressions; two options are available:

1) Make Mapping a functional interface and get rid of the (unused) name field
2) Tweak the Mapping constructor so as to take a Function<Type, Type>

Let's see how the above code snipped would change in both options:

1) functional interface

            Mapping boxMap = t -> types.boxedTypeOrType(t);

2) lambda-friendly constructor:

           Mapping boxMap = new Mapping("boxMap", t -> types.boxedTypeOrType(t));