publicclass Cat {
publicvoid beFeeded(Person p){
p.feed(this);
}
}
publicclass WhiteCat extends Cat {
publicvoid beFeeded(Person p){
p.feed(this);
}
}
publicclass BlackCat extends Cat {
publicvoid beFeeded(Person p){
p.feed(this);
}
}
publicclass Person {
publicvoid feed(Cat cat) {
System.out.println("Person feedcat");
}
publicvoid feed(WhiteCat cat) {
System.out.println("Person feedWhiteCat");
}
publicvoid feed(BlackCat cat) {
System.out.println("Person feedBlackCat");
}
}
publicclass Man extends Person {
publicvoid feed(Cat cat) {
System.out.println("Man feedcat");
}
publicvoid feed(WhiteCat cat) {
System.out.println("Man feedWhiteCat");
}
publicvoid feed(BlackCat cat) {
System.out.println("Man feedBlackCat");
}
}
publicclass Woman extends Person {
publicvoid feed(Cat cat) {
System.out.println("Woman feedcat");
}
publicvoid feed(WhiteCat cat) {
System.out.println("Woman feedWhiteCat");
}
publicvoid feed(BlackCat cat) {
System.out.println("Woman feedBlackCat");
}
}
publicclass Client {
// 一個方法包括三部分：方法的接受者、方法名、方法的參數簽名（包括參數類型、參數個數、參數順序）。
// 其中方法的接受者與方法簽名稱爲方法的宗量
publicstaticvoid main(String[]args) {
test1();//說明動態分派
test2();//說明動態單分派
test3();//使用反轉球實現兩次動態單分派
}
publicstaticvoid test1(){
Cat cat = new Cat();//可用下面兩條語句替代，對結果無影響
// Cat cat = new BlackCat();
// Cat cat = new WhiteCat();
Person p;
p = new Person();
p.feed(cat);
p = new Man();
p.feed(cat);
p = new Woman();
p.feed(cat);
// Java語言調用期發生了向下轉型，就是動態分派了。也就是常說的多態
// 運行結果：
// Person feed cat
// Man feed cat
// Woman feed cat
}
publicstaticvoid test2(){
Cat cat = new Cat();
Cat bc = new BlackCat();
Cat wc = new WhiteCat();
Person p;
p = new Person();
p.feed(cat);
p.feed(bc);
p.feed(wc);
p = new Man();
p.feed(cat);
p.feed(bc);
p.feed(wc);
p = new Woman();
p.feed(cat);
p.feed(bc);
p.feed(wc);
// 不論參數爲Cat的任何子類型，都不會被考慮，因此Java語言只考慮接受者這個宗量，因此是動態單分派
// 運行結果：
// Person feed cat
// Person feed cat
// Person feed cat
// Man feed cat
// Man feed cat
// Man feed cat
// Woman feed cat
// Woman feed cat
// Woman feed cat
}
publicstaticvoid test3(){
Cat cat = new Cat();
Cat blackCat = new BlackCat();
Cat whiteCat = new WhiteCat();
Person p = new Person();
Person man = new Man();
Person woman = new Woman();
cat.beFeeded(p);
blackCat.beFeeded(p);
whiteCat.beFeeded(p);
cat.beFeeded(man);
blackCat.beFeeded(man);
whiteCat.beFeeded(man);
cat.beFeeded(woman);
blackCat.beFeeded(woman);
whiteCat.beFeeded(woman);
// 出發兩次動態單分派
// Person feed cat
// Person feed BlackCat
// Person feed WhiteCat
// Man feed cat
// Man feed BlackCat
// Man feed WhiteCat
// Woman feed cat
// Woman feed BlackCat
// Woman feed WhiteCat
}
}