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CovariantReturn.java
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41 lines (36 loc) · 782 Bytes
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// polymorphism/CovariantReturn.java
// (c)2021 MindView LLC: see Copyright.txt
// We make no guarantees that this code is fit for any purpose.
// Visit http://OnJava8.com for more book information.
class Grain {
@Override public String toString() {
return "Grain";
}
}
class Wheat extends Grain {
@Override public String toString() {
return "Wheat";
}
}
class Mill {
Grain process() { return new Grain(); }
}
class WheatMill extends Mill {
@Override Wheat process() {
return new Wheat();
}
}
public class CovariantReturn {
public static void main(String[] args) {
Mill m = new Mill();
Grain g = m.process();
System.out.println(g);
m = new WheatMill();
g = m.process();
System.out.println(g);
}
}
/* Output:
Grain
Wheat
*/