64 lines
1.7 KiB
Java
64 lines
1.7 KiB
Java
// generics/BasicBounds.java
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// (c)2017 MindView LLC: see Copyright.txt
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// We make no guarantees that this code is fit for any purpose.
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// Visit http://OnJava8.com for more book information.
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interface HasColor { java.awt.Color getColor(); }
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class WithColor<T extends HasColor> {
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T item;
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WithColor(T item) { this.item = item; }
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T getItem() { return item; }
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// The bound allows you to call a method:
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java.awt.Color color() { return item.getColor(); }
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}
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class Coord { public int x, y, z; }
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// This fails. Class must be first, then interfaces:
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// class WithColorCoord<T extends HasColor & Coord> {
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// Multiple bounds:
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class WithColorCoord<T extends Coord & HasColor> {
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T item;
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WithColorCoord(T item) { this.item = item; }
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T getItem() { return item; }
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java.awt.Color color() { return item.getColor(); }
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int getX() { return item.x; }
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int getY() { return item.y; }
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int getZ() { return item.z; }
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}
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interface Weight { int weight(); }
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// As with inheritance, you can have only one
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// concrete class but multiple interfaces:
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class Solid<T extends Coord & HasColor & Weight> {
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T item;
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Solid(T item) { this.item = item; }
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T getItem() { return item; }
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java.awt.Color color() { return item.getColor(); }
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int getX() { return item.x; }
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int getY() { return item.y; }
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int getZ() { return item.z; }
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int weight() { return item.weight(); }
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}
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class Bounded
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extends Coord implements HasColor, Weight {
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@Override
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public java.awt.Color getColor() { return null; }
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@Override
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public int weight() { return 0; }
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}
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public class BasicBounds {
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public static void main(String[] args) {
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Solid<Bounded> solid =
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new Solid<>(new Bounded());
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solid.color();
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solid.getY();
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solid.weight();
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}
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}
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