多态的应用-多态数组

多态的应用-多态数组

• 多态数组
  • 数组的定义类型为父类型，里面保存的实际元素类型是子类类型
• 多态参数
  • 方法定义的形参类型为父类型，实参类型允许为子类型

多态数组

应用实例：现有一继承结构如下：要求创建1个Person对象。2个 Student 对象和2个Teacher 对象，统一放在数组中，并调用 say方法。应用实例升级：如果调用子类特有的方法，比如 Teacher 有一个 teach，Student 有一个 study 调用。

Person.java

public class Person{
	private String name;
	private int age;

	public Person(String name, int age){
		this.name = name;
		this.age = age;
	}

	public void setname(String name){
		this.name = name;
	}

	public String getname(){
		return name;
	}

	public void setage(int age){
		this.age = age;
	}

	public int getage(){
		return age;
	}

	public String say(){
		return name + "\t" + age;
	}
}

Student.java

public class Student extends Person{
	private double score;

	public Student(String name, int age, double score){
		super(name, age);
		this.score = score;
	}

	public void setscore(int score){
		this.score = score;
	}

	public double getscore(){
		return score;
	}

	// Override Person say
	public String say(){
		return super.say()+" score "+ score;
	}

}

Teacher.java

public class Teacher extends Person{
	private double salary;

	public Teacher(String name, int age, double salary){
		super(name, age);
		this.salary = salary;
	}

	public void setsalary(){
		this.salary = salary;
	}

	public double getsalary(){
		return salary;
	}

	// Override Person say
	public String say(){
		return super.say() + " salary" + salary;
	}

}

mains.java

public class mains{
	public static void main(String[] args) {

		Person[] persons = new Person[5];

		persons[0] = new Person("jack", 20);
		persons[1] = new Student("jack", 20, 100);
		persons[2] = new Student("smith", 20, 60);
		persons[3] = new Teacher("scott", 40, 40000);
		persons[4] = new Teacher("king", 50, 50000);

		for (int i = 0;  i < persons.length; i++) {
			// Person[i] 的编译类型是 Person ，运行类型根据实际的情况由 jvm 来判断
			System.out.println(persons[i].say());
		}
	}
}

jack    20
jack    20 score 100.0
smith   20 score 60.0
scott   40 salary40000.0
king    50 salary50000.0