64 lines
1.7 KiB
Java
64 lines
1.7 KiB
Java
// generics/BasicBounds.java
|
|
// (c)2020 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.
|
|
|
|
interface HasColor { java.awt.Color getColor(); }
|
|
|
|
class WithColor<T extends HasColor> {
|
|
T item;
|
|
WithColor(T item) { this.item = item; }
|
|
T getItem() { return item; }
|
|
// The bound allows you to call a method:
|
|
java.awt.Color color() { return item.getColor(); }
|
|
}
|
|
|
|
class Coord { public int x, y, z; }
|
|
|
|
// This fails. Class must be first, then interfaces:
|
|
// class WithColorCoord<T extends HasColor & Coord> {
|
|
|
|
// Multiple bounds:
|
|
class WithColorCoord<T extends Coord & HasColor> {
|
|
T item;
|
|
WithColorCoord(T item) { this.item = item; }
|
|
T getItem() { return item; }
|
|
java.awt.Color color() { return item.getColor(); }
|
|
int getX() { return item.x; }
|
|
int getY() { return item.y; }
|
|
int getZ() { return item.z; }
|
|
}
|
|
|
|
interface Weight { int weight(); }
|
|
|
|
// As with inheritance, you can have only one
|
|
// concrete class but multiple interfaces:
|
|
class Solid<T extends Coord & HasColor & Weight> {
|
|
T item;
|
|
Solid(T item) { this.item = item; }
|
|
T getItem() { return item; }
|
|
java.awt.Color color() { return item.getColor(); }
|
|
int getX() { return item.x; }
|
|
int getY() { return item.y; }
|
|
int getZ() { return item.z; }
|
|
int weight() { return item.weight(); }
|
|
}
|
|
|
|
class Bounded
|
|
extends Coord implements HasColor, Weight {
|
|
@Override
|
|
public java.awt.Color getColor() { return null; }
|
|
@Override
|
|
public int weight() { return 0; }
|
|
}
|
|
|
|
public class BasicBounds {
|
|
public static void main(String[] args) {
|
|
Solid<Bounded> solid =
|
|
new Solid<>(new Bounded());
|
|
solid.color();
|
|
solid.getY();
|
|
solid.weight();
|
|
}
|
|
}
|