Question

Which approach would be better between the following two?
I have chosen enums since, in the typical case subtype polymorphishm is the best approach; also this is a typical approach when writing a simple factory method.

public class SomeClass {
    public SomeEnum returnAType(String someString) {
        //implementation bellow
   }

   private boolean method1() {
   //...
   }

   private boolean method2() {
   //...
   }

   private boolean method3() {
   //...
   }

}

The first implementation of returnATypeMethod; this is faster since it does not call method2 and method3 (and possibly more) if method1 is valid.

    public SomeEnum returnAType(String someString) {
        if(method1(someString)) {
            SomeEnum.ENUM1.doSomething();
            return SomeEnum.ENUM1;
        }
        if(method2(someString)) {
            SomeEnum.ENUM2.doSomething();
            return SomeEnum.ENUM2;
        }
        if(method3(someString)) {
            SomeEnum.ENUM3.doSomething();
            return SomeEnum.ENUM3;
        }
        SomeEnum.DEFAULT_ENUM.doSomething();
        return SomeEnum.DEFAULT_ENUM;
   }

The second implementation of returnATypeMethod; this is more clear and no code duplicate:

    public SomeEnum returnAType(String someString) {
        SomeEnum enumType = SomeEnum.DEFAULT_ENUM;
        if(method1(someString)) {
            enumType = SomeEnum.ENUM1;
        }
        if(method2(someString)) {
            enumType = SomeEnum.ENUM2;            }
        }
        if(method3(someString)) {
            enumType = SomeEnum.ENUM3;
        }
        enumType.doSomething();
        return enumType;
   }

Answer 1

I would be tempted to use

public SomeEnum returnAType(String someString) {
    SomeEnum enumType = method1(someString) ? SomeEnum.ENUM1 :
                        method2(someString) ? SomeEnum.ENUM2 :
                        method3(someString) ? SomeEnum.ENUM3 : SomeEnum.DEFAULT_ENUM;
    enumType.doSomething();
    return enumType;

}