接口、繼承、抽象類

AllOop.java

import java.util.*;
import face.*;//自定義的包  
import love.*;//同上
import javax.swing.*;

public class AllOop {
	/**abstract instanceof extends interfacce implements final super等關鍵字
	 * @param args
	 */
	public static void main(String[] args) {
		oop();
	}
	
	public static void oop() {
		
		Top top = new Top();
		LiangYin ai = new LiangYin(520.1314);
		ai.look();
		System.out.print("Please enter the name of company: ");
		String cName = input.nextLine();
		System.out.print("Please enter the address of company: ");
		String cAddress = input.nextLine();
		System.out.print("Please count the number of employee: ");
		int cPerson = input.nextInt();
		Company company = new Company(cName, cAddress, cPerson);
		tu(company);
		Employee employee = new Employee(cName, cAddress, cPerson, 123.4, "liuwei", 25);
		Employee employee1 = new Employee(cName, cAddress, cPerson, 123.4, "liuwei", 25);
		System.out.println(employee.equals(employee1));
		tu(employee);
		paying(employee);
		System.out.println(employee.toBack());
		employee.doSomething();
	}
	//多態性，動態綁定
	public static void tu(Eepay x)
	{
		x.output();
	}
	public static void paying(Pay x)
	{
		System.out.println(x.allPay());
	}
	private static Scanner input = new Scanner(System.in);
}

interface Eepay//定義接口
{
	public int num();
	public void output();
}

interface Pay
{
	public double allPay();
}


class Company implements Eepay//實現接口
{
public Company() {}

public Company(String name, String address, int numPerson) {
	this.name = name;
	this.address = address;
	this.numPerson = numPerson;
}

public int num() {
	return (int)Math.pow(numPerson, 2);
}

public void output() {
	System.out.println(name + " " + address + " " + numPerson);
}

public String toString()
{
	return name + " " + address;
}

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

public String getAddress() {return address;}
public void setAddress(String address) {this.address = address;}

public int getNumPerson() {return numPerson;}
public void setNumPerson(int numPerson) {this.numPerson = numPerson;}

private String name;//公司名
private String address;//地址
private int numPerson;//公司員工數
}


final class Employee extends Company implements Eepay, Pay, Wei//final修飾符，最後的類，不能擴展的類
{
public Employee(){}
public Employee(String name, String address, int numPerson,
		double priceHour, String eName, int age)
{
	super(name, address, numPerson);
	this.priceHour = priceHour;
	this.seteName(eName);
	this.setAge(age);
}

public boolean equals(Object obj)//重寫Object類的equals方法
{
	if (obj == null) return false;
	else
	{
		if (obj instanceof Employee)
		{
			Employee e = (Employee)obj;
			return e.age == this.age && e.eName == this.eName && e.priceHour == this.priceHour;
		}
	}
	return false;
}
public void doSomething()
{
	System.out.println(eName + " " + age + " " + priceHour);
}
public String toBack()
{
	return super.getAddress() + super.getName();
}
public int num()
{
	return (int)(age*this.allPay());
}
public void output()
{
	System.out.println(eName + " " + age + " " + priceHour);
}
public double allPay() {
	double all = super.getNumPerson() * priceHour;
	return all;
}
public int getAge() {
	return age;
}
public void setAge(int age) {
	this.age = age;
}
public String geteName() {
	return eName;
}
public void seteName(String eName) {
	this.eName = eName;
}
private double priceHour;
private String eName;
private int age;
}

class LiangYin extends You
{
	public LiangYin(){}
	public LiangYin(double sun)
	{
		super(sun);
	}
	
	public void look()
	{
		System.out.println(this.getSun());
	}
}

 

package包

 

Top.java

package face;

public class Top {
	public Top()
	{
		System.out.println("Good luck!Student!");
	}
}

wei.java

package face;

public interface Wei//接口單獨寫一個包時必須聲明public而且文件名與接口名一致
{
	public String toBack();
}

 

you.java

package love;

public abstract class You//抽象類
{
	public You(){}
	public You(double sun) {
		this.setSun(sun);
	}
	
	public abstract void look();
	
	public double getSun() {
		return sun;
	}
	public void setSun(double sun) {
		this.sun = sun;
	}

	private double sun;
	private static int NUM = 1;
	
	static {
		NUM = 100 * NUM;
	}
}

抽象類，不允許創建對象的類，只需要在class前面加上abstract關鍵字；

在java中，一個類只能有一個超類，也就是父類，可以有多個子類，繼承的關鍵字是extends，這樣就不能像C++那樣有多繼承的出現；

而接口，恰恰可以解決將java中不能多繼承的問題，繼承接口的關鍵字是implements，創建接口的關鍵字是interface，類和接口都可以繼承多個接口。