①Object类是所有类的最终祖先，Java中的每个类都由Object类继承而来，但在定义类的时候，不需要显式说明该类继承自Object。所有的对象都可以写成：  Object o = new aClass();。
②除了基本数据类型，Java中所有的都是对象，包括我们常见的一个方法，一个变量，常量，还有参数都可以表示成一个对象。

package com.object.test;

import java.util.Date;

public class Employee {
	
	int id;
	String name;
	int age;
	double salary;
	String position;
	Date birthday;
	Employee()
	{
		super();
	}
	
	Employee(int id,String name,int age,double salary,String positon,Date birhtday)
	{
		this.id=id;
		this.name=name;
		this.age=age;
		this.salary=salary;
		this.position=positon;
		this.birthday=birhtday;
	}

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	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 double getSalary() {
		return salary;
	}

	public void setSalary(double salary) {
		this.salary = salary;
	}

	public String getPosition() {
		return position;
	}

	public void setPosition(String position) {
		this.position = position;
	}
	@Override 
	public boolean equals(Object otherObject)
	{
		//检测otherObject是否是空引用
		if(otherObject==null)
		{
			return false;
		}
		//检查this和otherObject是否引用同一个对象那个
		if(this==otherObject)
		{
			return true;
		}
		//检测otherObject是否是Employee类的对象或者是子类对象。
		if(!(otherObject instanceof Employee))
		{
			return false;
		}
		/*if(!(this.getClass()==otherObject.getClass()))
		{
			return false;
		}*/
		Employee e =(Employee)otherObject;
		
		if(this.id==e.id&&this.name==e.name&&this.age==e.age&&this.salary==e.salary&&this.position==e.position&&this.birthday.equals(e.birthday))
		{
			return true;
		}else
		{
			return false;
		}
		
	}

	@Override
	public int hashCode() {
		
		return (int) (1*this.id+2*this.age+3*this.salary);
	}
	
	
	
	

}


class Manager extends Employee
{
	double bonus;
	Manager(int id,String name,int age,double salary,String position,Date birthday)
	{
		super(id,name,age,salary,position,birthday);
	}
	Manager(int id,String name,int age,double salary,String position,Date birthday,double bonus)
	{
		super(id,name,age,salary,position,birthday);
		this.bonus=bonus;
	}
	
	

	@Override 
	public boolean equals(Object otherObject)
	{
		
		if(!(super.equals(otherObject)))
		{
					return false;
		}else
		{
			Manager m =(Manager)otherObject;
			return this.bonus==m.bonus;
		}
		
		
	}
	@Override
	public int hashCode() {
		
		return	super.hashCode()+4*(int)bonus;
	}
	
	
	
	
}

package com.object.test;

import java.util.Date;

public class TestCalss {
public static void main(String[] args) {
		
		Employee em1= new Employee(1,"xiaowang",23,3000.0,"A",new Date(10000));
		Employee em2= new Employee(1,"xiaowang",23,3000.0,"A",new Date(10000));
		Manager m1 =new Manager(1,"xiaowang",23,3000.0,"A",new Date(10000));
		Manager m2 =new Manager(1,"xiaowang",23,3000.0,"A",new Date(10000));
		System.out.println(em1.equals(em2));
		System.out.println(m1.equals(m2));
		System.out.println(em1.equals(m1));
		System.out.println(em1.hashCode()==em2.hashCode());
		System.out.println(em1.hashCode()==m1.hashCode());
	}

}