如果你想设计这样一个类，该类包含一个特别的成员方法，该方法的具体实现由它的子类确定，那么你可以在父类中声明该方法为抽象方法。

public abstract class Employee
{
    private String name;
    private String address;
    private int number;

    public abstract double computePay();

    //其余代码
}

public class Salary extends Employee
{
    private double salary; // Annual salary

    public double computePay()
    {
        System.out.println("Computing salary pay for " + getName());
        return salary/52;
    }

    //其余代码
}