OnJava8-Examples/generics/FactoryConstraint.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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// generics/FactoryConstraint.java

// We make no guarantees that this code is fit for any purpose.

// Visit http://OnJava8.com for more book information.

import java.util.*;

import java.util.function.*;

import onjava.*;

class IntegerFactory implements Supplier<Integer> {

private int i = 0;

@Override public Integer get() {

return ++i;

}

class Widget {

private int id;

Widget(int n) { id = n; }

@Override public String toString() {

return "Widget " + id;

}

public static

class Factory implements Supplier<Widget> {

private int i = 0;

@Override

public Widget get() { return new Widget(++i); }

}

class Fudge {

private static int count = 1;

private int n = count++;

@Override public String toString() {

return "Fudge " + n;

}

class Foo2<T> {

private List<T> x = new ArrayList<>();

Foo2(Supplier<T> factory) {

Suppliers.fill(x, factory, 5);

}

@Override public String toString() {

return x.toString();

}

public class FactoryConstraint {

public static void main(String[] args) {

System.out.println(

new Foo2<>(new IntegerFactory()));

System.out.println(

new Foo2<>(new Widget.Factory()));

System.out.println(

new Foo2<>(Fudge::new));

}

/* Output:

[1, 2, 3, 4, 5]

[Widget 1, Widget 2, Widget 3, Widget 4, Widget 5]

[Fudge 1, Fudge 2, Fudge 3, Fudge 4, Fudge 5]

OnJava8-Examples/generics/FactoryConstraint.java at master · CSapprenticeWT/OnJava8-Examples · GitHub

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