jsweet.util.union

Interface Union<T1,T2>

Type Parameters:

T1 -

T2 -

All Known Subinterfaces:

Union3<T1,T2,T3>, Union4<T1,T2,T3,T4>, Union5<T1,T2,T3,T4,T5>, Union6<T1,T2,T3,T4,T5,T6>

public interface Union<T1,T2>

This interface is an auxiliary type used by JSweet to define union types.

A union type is a type which can be cast to one of its union-ed types. For instance:

 Union<String, Number> u = ...;
 String s = union(u);
 // or:
 Number n = union(u);
 

Note that Java will not complain when casting to a type that is not part of the union, but the JSweet transpiler will.

 Union<String, Number> u = ...;
 Date d = union(u); // compiles in pure Java, but not in JSweet
 

When a method expects a union, such as the following m method:

 void m(Union<String, Number> p);
 

Then it can be called with a String or a Number, by first translating to a union:

 String s = ...
 m(union(s));
 

In case of union types of more than two types, one can extend the Union interface for accepting more type parameters. For instance, to define a union type that takes 3 arguments, just write:

 public interface Union3 extends Union {
 }
 

Author:

Renaud Pawlak