Referring to a current type using Java generics -

i have interface type parameter allows conversion same type type parameter. this:

interface interfaze<a> {     public <b> interfaze<b> convert(java.util.function.function<a, b> f); } 

i want impose stricter requirement on return type: want convert method return same type called on. this:

class goodinterfaze<a> implements interfaze<a> {     public <b> interfaze<b> convert(java.util.function.function<a, b> f) {         // return new goodinterfaze<b>();     // want allowed compiler         // return new badinterfaze<b>();      // want compilation error          return null;     } }  class badinterfaze<a> implements interfaze<a> {     public <b> interfaze<b> convert(java.util.function.function<a, b> f) {         // return new goodinterfaze<b>();     // want compilation error         // return new badinterfaze<b>();      // want allowed compiler          return null;     } } 

the interfaze interface under control, can add type parameters (or methods) when needed. java generics allow this?

you can close doing this.

public interface interfaze<t extends interfaze<t>> {      t convert(); } 

then can do

public class main {      public static class implements interfaze<good> {          @override         public convert() { return new good(); } // compiles     }      public static class bad implements interfaze<bad> {          @override         public bad convert() { return new good(); } // doesn't compile     } } 

this idea of using recursive bounds common. dislike it's confusing , because doesn't mix inheritance. example, can't make subclass subgood of good implements interfaze<subgood> because can't implement same generic interface 2 different type arguments. works if implementing classes cannot extended (that's why enum<e extends enum<e>> ok).