Java 多态，

Java 多态，

多态是同一个行为具有多个不同表现形式或形态的能力。

多态性是对象多种表现形式的体现。

查看例子：

/* 文件名 : Employee.java */
public class Employee {
   private String name;
   private String address;
   private int number;
   public Employee(String name, String address, int number) {
      System.out.println("Constructing an Employee");
      this.name = name;
      this.address = address;
      this.number = number;
   }
   public void mailCheck() {
      System.out.println("Mailing a check to " + this.name
       + " " + this.address);
   }
   public String toString() {
      return name + " " + address + " " + number;
   }
   public String getName() {
      return name;
   }
   public String getAddress() {
      return address;
   }
   public void setAddress(String newAddress) {
      address = newAddress;
   }
   public int getNumber() {
     return number;
   }
}

---

/* 文件名 : Salary.java */
public class Salary extends Employee {
   private double salary; //Annual salary
   public Salary(String name, String address, int number, double
      salary) {
       super(name, address, number);
       setSalary(salary);
   }
   public void mailCheck() {
       System.out.println("Within mailCheck of Salary class ");
       System.out.println("Mailing check to " + getName()
       + " with salary " + salary);
   }
   public double getSalary() {
       return salary;
   }
   public void setSalary(double newSalary) {
       if(newSalary >= 0.0)
       {
          salary = newSalary;
       }
   }
   public double computePay() {
      System.out.println("Computing salary pay for " + getName());
      return salary/52;
   }
}

---

/* 文件名 : VirtualDemo.java */
public class VirtualDemo {
   public static void main(String [] args) {
      Salary s = new Salary("Mohd Mohtashim", "Ambehta, UP", 3, 3600.00);
      Employee e = new Salary("John Adams", "Boston, MA", 2, 2400.00);
      System.out.println("Call mailCheck using Salary reference --");
      s.mailCheck();
      System.out.println("\n Call mailCheck using Employee reference--");
      e.mailCheck();
    }
}

---

运行结果：

Constructing an Employee
Constructing an Employee
Call mailCheck using Salary reference --
Within mailCheck of Salary class
Mailing check to Mohd Mohtashim with salary 3600.0

Call mailCheck using Employee reference--
Within mailCheck of Salary class
Mailing check to John Adams with salary 2400.0