Java语言静态多分派 与 动态单分派
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 {
// 一个方法包括三部分：方法的接受者、方法名、方法的参数签名（包括参数类型、参数个数、参数顺序）。
// 其中方法的接受者与方法签名称为方法的宗量
publicstaticvoid main(String[]args) {
test1();//说明动态分派
test2();//说明动态单分派
test3();//使用反转球实现两次动态单分派
}
publicstaticvoid test1(){
Cat cat = new Cat();//可用下面两条语句替代，对结果无影响
// 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语言调用期发生了向下转型，就是动态分派了。也就是常说的多态
// 运行结果：
// 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);
// 不论参数为Cat的任何子类型，都不会被考虑，因此Java语言只考虑接受者这个宗量，因此是动态单分派
// 运行结果：
// 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);
// 出发两次动态单分派
// 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
}
}