1월 25일(수) - 7장(자바 날개 달기)

7장 - 자바 날개 달기

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ

 

7-1 패키지

// 7-1 패키지
import house.HouseKim;

public class Sample{
    public static void main(String[] args){
        HouseKim kim = new HouseKim();
    }
}

import house.*;

public class Sample{
    public static void main(String[] args){
        HouseKim kim = new HouseKim();
        HousePark park = new HousePark();
    }
}

 

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ

 

7-2 접근제어자

1) private

// 7-2 private 접근제어자
public class Sample{
    private String secret;
    private String getSecret(){
        return this.secret;
    }
}

2) default

// 7-2 default 접근제어자
package house;

public class HouseKim {
    String lastname = "kim";
}

// 7-2 default 접근제어자

package house;
public class HousePark {
    String lastname = "park";
    public static void main(String[] args){
        HouseKim kim = new HouseKim();
        System.out.println(kim.lastname);
    }
}

3) protected

// 7-2 protected 접근제어자
package house;
public class HousePark{
    protected String lastname = "park";
}

// protected 접근제어자
package house.person;
import house.HousePark;

public class EungYongPark extends HousePark{
    public static void main(String[] args){
        EungYongPark eyp = new EungYongPark();
        System.out.println(eyp.lastname);
    }
}

4) public

// 7-2 public 접근제어자
package house;
public class HousePark{
    protected String lastname = "park";
    public String info = "this is public message.";
}

// public 접근제어자
import house.HousePark;
public class Sample{
    public static void main(String[] args){
        HousePark housePark = new HousePark();
        System.out.println(housePark.info);
    }
}

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ

 

7-3 스태틱

1) static 변수

// 7-3 static 변수
class Counter{
    static int count=0;
    Counter(){
        count++;
        System.out.println(count);
    }
}

public class Sample{
    public static void main(String[] args){
        Counter c1 = new Counter();
        Counter c2 = new Counter();
    }
}

2) static 메서드

// 7-3 static 메서드
class Counter{
    static int count=0;
    Counter(){
        count++;
        System.out.println(count);
    }
    public static int getCount(){
        return count;
    }
}

public class Sample{
    public static void main(String[] args){
        Counter c1 = new Counter();
        Counter c2 = new Counter();

        System.out.println(Counter.getCount());
    }
}

//
import java.text.SimpleDateFormat;
import java.util.Date;

class Utill{
    public static String getCurrentDate(String fmt){
        SimpleDateFormat sdf = new SimpleDateFormat(fmt);
        return sdf.format(new Date());
    }
}

public class Sample{
    public static void main(String[] args){
        System.out.println(Utill.getCurrentDate("yyyyMMdd"));
    }
}

3) 싱글톤 패턴

//7-3 싱글톤 패턴
class Singleton{
    private static Singleton one;
    private Singleton(){

    }
    public static Singleton getInstance(){
        if(one == null){
            one = new Singleton();
        }
        return one;
    }
}

public class Sample{
    public static void main(String[] args){
        Singleton singleton1 = Singleton.getInstance();
        Singleton singleton2 = Singleton.getInstance();
        System.out.println(singleton1 == singleton2);
    }
}

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ

 

7-4 예외처리

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ

 

7-5 쓰레드

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ

 

7-6 함수형 프로그래밍

ㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡㅡ