在学习泛型中遇到的多态的一个小问题

在学习泛型的过程中，我需要创建person、worker、student 一个父类两个子类，但是在创建过程遇到一些问题，先上代码

package cn.haiyisoft.domain;

public class PersonForGeneric implements Comparable<PersonForGeneric> {

	private String name;
	private int age;

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

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

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + age;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		PersonForGeneric other = (PersonForGeneric) obj;
		if (age != other.age)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}

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

	public PersonForGeneric() {
		super();
	}

	@Override
	public int compareTo(PersonForGeneric o) {
		// TODO Auto-generated method stub
		if (this.getName().equals(o.getName()))
			return this.getAge() - o.getAge();
		else
			return this.getName().compareTo(o.getName());

	}

}

package cn.haiyisoft.domain;

public class WorkerForGeneric extends PersonForGeneric {

	private String name;
	private int age;

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

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

	

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

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = super.hashCode();
		result = prime * result + age;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (!super.equals(obj))
			return false;
		if (getClass() != obj.getClass())
			return false;
		WorkerForGeneric other = (WorkerForGeneric) obj;
		if (age != other.age)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}

	@Override
	public String toString() {
		return "WorkerForGeneric [name=" + name + ", age=" + age + "]";
	}

		
	
	}

package cn.haiyisoft.domain;

public class StudentForGeneric extends PersonForGeneric {

	private String name;

	private int age;

	public String getName() {
		return name;
	}

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

	public int getAge() {
		return age;
	}

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

	@Override
	public int hashCode() {
		final int prime = 31;
		int result = 1;
		result = prime * result + age;
		result = prime * result + ((name == null) ? 0 : name.hashCode());
		return result;
	}

	@Override
	public boolean equals(Object obj) {
		if (this == obj)
			return true;
		if (obj == null)
			return false;
		if (getClass() != obj.getClass())
			return false;
		StudentForGeneric other = (StudentForGeneric) obj;
		if (age != other.age)
			return false;
		if (name == null) {
			if (other.name != null)
				return false;
		} else if (!name.equals(other.name))
			return false;
		return true;
	}

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

	@Override
	public String toString() {
		return "StudentForGeneric [name=" + name + ", age=" + age + "]";
	}

	
}

person类实现了comparable接口，worker和student类继承了person类，按照正常的设计来讲，worker和student类不需要再定义name。age以及相应的set和get方法，但是我在两个类里又重新定义了name和age 这就导致了person类中的compareto方法有了些问题

正常来讲compareto方法里面应该是这样的

public int compareTo(PersonForGeneric o) {
		// TODO Auto-generated method stub
		if (this.name.equals(o.name))
			return this.age - o.age;
		else
			return this.name.compareTo(o.name);

	}

但是如果在treeset中传入子类，那么就会使得this.name等指向了父类的name，但是父类的name是没有被赋值的（成员变量没有多态）最后运行时会报空指针，如果一定要坚持的话，那么compareto方法要改成这样

public int compareTo(PersonForGeneric o) {
		// TODO Auto-generated method stub
		if (this.getName().equals(o.getName()))
			return this.getAge() - o.getAge();
		else
			return this.getName().compareTo(o.getName());

	}