Java: Method chaining in derived class -

i writing derivedclass (extends superclass) method chaining. example,

public class superclass {     protected int responsecode;     protected string responsemessage;      public void setresponsecode(int code) {             this.responsecode = code;     }      public int getresponsecode() {             return responsecode;     }      public superclass withresponsecode(int code) {             setresponsecode(code);             return this;     }      public void setresponsemessage(string message) {             this.responsemessage = message;     }      public string getresponsemessage() {             return responsemessage;     }      public superclass withresponsemessage(string message) {             setresponsemessage(message);             return this;     } 

}

and

public class derivedclass extends superclass {     protected string credentialtype;     protected string credentialid;      public void setcredentialtype(string type) {             this.credentialtype = type;     }      public string getcredentialtype() {             return credentialtype;     }      public derivedclass withcredentialtype(string type) {             setcredentialtype(type);             return this;     }       public void setcredentialid(string id) {             this.credentialid = id;     }      public string getcredentialid() {             return credentialid;     }      public derivedclass withcredentialid(string id) {             setcredentialid(id);             return this;     }      public static void main(string[] args) {             derivedclass dc = new derivedclass();             /*dc.setresponsecode(200);             dc.setresponsemessage("success");             dc.setcredentialtype("mobileidentifier");             dc.setcredentialid("678882");*/              dc.withresponsecode(200)                     .withresponsemessage("success")                     .withcredentialtype("mobileidentifier")                     .withcredentialid("678882");              system.out.println("derived class: code - " + dc.getresponsecode() + " - response message - " + dc.getresponsemessage() + " - credential type - " + dc.getcredentialtype());     } 

}

during compilation of above getting:

derivedclass.java:41: error: cannot find symbol                     .withcredentialtype("mobileidentifier")                     ^ symbol:   method withcredentialtype(string) location: class superclass 1 error 

why getting when credentialtype field in derivedclass , not in superclass? how can chain mixed methods superclass & derivedclass using derivedclass object?

as others have stated, getting compilation error because methods of superclass return superclass type, doesn't contain derivedclass's methods.

the correct way solve make superclass abstract , use generics on superclass recursive type (also called f-bound type):

public abstract class superclass<t extends superclass<t>> {      // todo attributes, getters , setters      public t withresponsecode(int code) {         setresponsecode(code);         return (t) this; // cast absolutely safe!     }      // todo other superclass builder methods } 

then, can define derivedclass follows:

public class derivedclass extends superclass<derivedclass> {      // todo attributes, getters , setters      public derivedclass withcredentialtype(string type) {         setcredentialtype(type);         return this;     }      // todo other derivedclass builder methods } 

and there won't more compilation errors. downside of approach forces make superclass class abstract, in order use derived classes.