public class Employee {

    private String name;

    private double salary;

    private LocalDate hireDay;

    public Employee(String n, double s, int year, int month, int day){

        this.name = n;

        this.salary =s;

        this.hireDay = LocalDate.of(year, month, day);

    }

    public String getName() {

        return name;

    }

    public double getSalary() {

        return salary;

    }

    public LocalDate getHireDay() {

        return hireDay;

    }

    public void raiseSalary(double byPercent){

        double raise = salary * byPercent / 100;

        this.salary += raise;

    }

}

class Manager extends Employee{

    private double bonus;

    public Manager(String n, double s, int year, int month, int day, double bonus){

        super(n,s,year,month,day);        //调用父类构造函数

        this.bonus = bonus;

    }

    public void setBonus(double bonus){

        this.bonus = bonus;

    }

    @Override

    public double getSalary(){

　　　　 //double baseSalary = this.salary;　　//Error  'salary' has private access in 'Employee'

　　　　 //double baseSalary = this.getSalary();　　//无限嵌套调用本身

        double baseSalary = super.getSalary();

        return baseSalary + bonus;

    }

}

public class Test1 {

    public static void main(String[] args) throws InterruptedException {

        Employee boss = new Manager("boss", 1000000, 2011, 5, 1, 500000);

        //boss.setBonus(600000);        编译错误，无法找到setBonus

        System.out.println(boss.getName());

        System.out.println(boss.getSalary());

    }

}

/**

 * Returns a hash code value for the object. This method is

 * supported for the benefit of hash tables such as those provided by

 * {@link java.util.HashMap}.

 * <p>

 * The general contract of {@code hashCode} is:

 * <ul>

 * <li>Whenever it is invoked on the same object more than once during

 *     an execution of a Java application, the {@code hashCode} method

 *     must consistently return the same integer, provided no information

 *     used in {@code equals} comparisons on the object is modified.

 *     This integer need not remain consistent from one execution of an

 *     application to another execution of the same application.

 * <li>If two objects are equal according to the {@code equals(Object)}

 *     method, then calling the {@code hashCode} method on each of

 *     the two objects must produce the same integer result.

 * <li>It is <em>not</em> required that if two objects are unequal

 *     according to the {@link java.lang.Object#equals(java.lang.Object)}

 *     method, then calling the {@code hashCode} method on each of the

 *     two objects must produce distinct integer results.  However, the

 *     programmer should be aware that producing distinct integer results

 *     for unequal objects may improve the performance of hash tables.

 * </ul>

 * <p>

 * As much as is reasonably practical, the hashCode method defined by

 * class {@code Object} does return distinct integers for distinct

 * objects. (This is typically implemented by converting the internal

 * address of the object into an integer, but this implementation

 * technique is not required by the

 * Java&trade; programming language.)

1. 这方法是用来优化hash tables的，例如 HashMap。

2. 只要对象数据没有改变（equals方法中使用的数据），不论什么时候去获取hashCode，都应该也一样。但不是不允许hashCode变化。

3.两个对象如果equals判定相等， 必须有相同的hashCode

4. 当equals判定两个对象不相等时，并不要求hashCode一定不相等。但是要明白，不同对象（equals比较）有不同的hashCode可以提高 哈希表的性能。

5. Object类的hashCode方法返回的是由地址转换的整型。不同对象hashCode不同。 它是native方法，其他语言实现的。

public boolean equals(Object otherObject)

{

   // a quick test to see if the objects are identical

   if (this == otherObject) return true;

   // must return false if the explicit parameter is null

   if (otherObject == null) return false;

   // if the classes don't match, they can't be equal

   if (getClass() != otherObject.getClass()) return false;

   // now we know otherObject is a non-null Employee

   Employee other = (Employee) otherObject;

   // test whether the fields have identical values

   return Objects.equals(name, other.name) && salary == other.salary && Objects.equals(hireDay, other.hireDay);

}

public int hashCode(){

    return 7 * Objects.hashCode(name) + 11 * new Double(salary).hashCode() + 13 * hireDay.hashCode();

}

或

public int hashCode()

{

   return Objects.hash(name, salary, hireDay);

}

Class类

getName()

getSuperclass()

getModifiers()

getFields()---返回public 数据，getDeclareFields ---返回所有数据-----Field类

getMethods()---返回public 方法， getDeclareMethods---返回所有方法---Method类

getConstructors()---返回public 构造器，getDeclareConstructors--返回所有构造器---Constructor类

newInstance()

static forName

  Field

getName()

getType()----返回类型，Class对象

getModifiers()

  Method

getName()

getReturnType()

getModifiers()

getParameterTypes()

  Constructor

getName()

getModifiers()

getParameterTypes()