?? music26.java
字號:
// typeinfo/music268/Music268.java
// TIJ4 Chapter Typeinfo, Exercise 26, page 615
// Implement clearSpitValve() as described in the summary.
/* Solution includes, in same package:
* import java.util.*;
* public class RandomInstrumentGenerator {
* private Random rand = new Random();
* public Instrument next() {
* switch(rand.nextInt(7)) {
* default:
* case 0: return new Wind();
* case 1: return new Percussion();
* case 2: return new Stringed();
* case 3: return new Keyboard();
* case 4: return new Brass();
* case 5: return new Woodwind();
* case 6: return new Piano();
* }
* }
* }
*/
package typeinfo.music26;
import polymorphism.music.Note;
import static net.mindview.util.Print.*;
class Instrument {
void play(Note n) { print("Instrument.play() " + n); }
public String toString() { return "Instrument"; }
void adjust() { print("Adjusting Instrument"); }
}
class Wind extends Instrument {
void play(Note n) { print("Wind.play() " + n); }
public String toString() { return "Wind"; }
void adjust() { print("Adjusting Wind"); }
void clearSpitValve() { print("Wind clearing spit valve"); }
}
class Percussion extends Instrument {
void play(Note n) { print("Percussion.play() " + n); }
public String toString() { return "Percussion"; }
void adjust() { print("Adjusting Percussion"); }
}
class Stringed extends Instrument {
void play(Note n) { print("Stringed.play() " + n); }
public String toString() { return "Stringed"; }
}
class Keyboard extends Instrument {
void play(Note n) { print("Keyboard.play() " + n); }
public String toString() { return "Keyboard"; }
void adjust() { print("Adjusting Keyboard"); }
}
class Brass extends Wind {
void play(Note n) { print("Brass.play() " + n); }
public String toString() { return "Brass"; }
void adjust() { print("Adjusting Brass"); }
void clearSpitValve() { print("Brass clearing spit valve"); }
}
class Woodwind extends Wind {
void play(Note n) { print("Woodwind.play() " + n); }
public String toString() { return "Woodwind"; }
void clearSpitValve() { print("Woodwind clearing spit valve"); }
}
class Piano extends Keyboard {
void play(Note n) { print("Piano.play() " + n); }
public String toString() { return "Piano"; }
}
public class Music26 {
// Doesn't care about type, so new types
// added to the system still work right:
public static void tune(Instrument i) {
//...
i.play(Note.MIDDLE_C);
}
public static void tuneAll(Instrument[] e) {
for(Instrument i : e)
tune(i);
}
private static RandomInstrumentGenerator gen = new RandomInstrumentGenerator();
public static void main(String[] args) {
// Upcasting during addition to the array:
Instrument[] orchestra = new Instrument[20];
// fill up orchestra array wth instruments:
for(int i = 0; i < orchestra.length; i++)
orchestra[i] = gen.next();
for(Instrument i : orchestra) {
if(i instanceof Wind) // get RTTI
((Wind)i).clearSpitValve();
i.adjust();
}
tuneAll(orchestra);
}
}
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