java abstract

简介

java 中的抽象类学习

code

main

package com;

public class PersonTest {
	public static void main(String[] args) {
		Person[] person = new Person[2];
		
		person[0] = new Employee("Harry Hacker", 5000, 1989, 10,1);
		person[1] = new Student("Maria Morris", "computer science");
		
		for(Person p : person)
			System.out.println(p.getName() + ", " + p.getDescription());
	}
}

abstract

package com;

public abstract class Person {
	public abstract String getDescription();
	private String name;
	
	public Person(String name) {
		this.name = name;
	}
	
	public String getName() {
		return name;
	}
}

Student

package com;

public class Student extends Person{
	private String major;
	/**
	 * @param name the student's name
	 * @param major the student's major 
	 */
	public Student(String name, String major) {
		super(name);
		this.major = major;
	}
	public String getDescription(){
		return "a student majoring in " + major;
	}
}

Employee

package com;

import java.util.Random;
import java.time.*;
class Employee extends Person{
	private double salary;
	private LocalDate hireDay;
	
	public Employee(String name, double salary, int year, int month, int day){
		super(name);
		this.salary = salary;
		hireDay = LocalDate.of(year, month, day);
	}
	
	public double getSalary() {
		return salary;
	}
	
	public LocalDate getHireDay() {
		return hireDay;
	}
	
	public String getDescription() {
		return String.format("an emplyee with a salary of $%.2f", salary);
	}
	
	public void raiseSalary(double byPercent) {
		double raise = salary * byPercent / 100;
		salary += raise;
	}
}

自问自答环节

QU: 抽象类能不能生成对象
AN：不能
QU：某类继承了抽象类，在什么情况加某类才不是抽象类
AN：实现了抽象类里面的函数覆盖