20201016_17 arraylist, map, 상속

==은 스택영역 값 비교

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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• ArrayList

package com.chap01;

import java.util.ArrayList;
import java.util.List;

public class Ex04 {

	public static void main(String[] args) {
		List<String> list = new ArrayList<String>();
		
		list.add("java");
		list.add("JDBC");
		list.add("C++");
		
		int size = list.size();
		
		for (int i = 0; i < list.size(); i++) {
			String str = list.get(i);
			System.out.println(i + ":" + str);
		}
	}

}

Animal an = new Cat();과 같은것임

 

 

 

 

 

 

package com.chap01;

import java.util.ArrayList;

public class Ex05 {

	public static void main(String[] args) {
		ArrayList<Info> list = new ArrayList<Info>();
		Info in = new Info();
		in.name = "hanna";
		in.number = 1234;
		
		list.add(in);
		
		Info in1 = new Info();
		in1.name = "김";
		
		list.add(in1);
		
		System.out.println(list.get(0).number);
		System.out.println(list.get(1).name);
	}
}

1234
김

 

 

 

 

 

 

 

• arraylist이용해 입력받고 출력하기

package com.chap01;

import java.util.ArrayList;
import java.util.Scanner;

public class Ex05 {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		ArrayList<Info> list = new ArrayList<Info>();
		Info in1 = new Info();
		in1.name = "hanna";
		in1.number = 1234;

		list.add(in1);
		for(;;) {
			System.out.println("-----MENU-----");
			System.out.println("(1) 입력");
			System.out.println("(2) 출력");
			System.out.println("--------------");

			int s = in.nextInt();

			if (s == 1) {
				Info in2 = new Info();
				System.out.print("이름 입력 : ");
				in2.name = in.next();
				list.add(in2);

				System.out.print("번호 입력 : ");
				in2.number = in.nextInt();
				list.add(in2);

			} else if (s ==2) {
				System.out.println("이름 : " + list.get(1).name);
				System.out.println("번호 : " + list.get(1).number);
				System.out.println("종료");

				return;
			}

		}
	}
}

-----MENU-----
(1) 입력
(2) 출력
--------------
1
이름 입력 : 김
번호 입력 : 20
-----MENU-----
(1) 입력
(2) 출력
--------------
2
이름 : 김
번호 : 20
종료

 

 

 

 

 

package com.chap01;

import java.util.ArrayList;
import java.util.Scanner;

public class Ex05 {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		ArrayList<Info> list = new ArrayList<Info>();
		Info in1 ;
		int count = 0;
		
		for(;;) {
			System.out.println("-----MENU-----");
			System.out.println("(1) 입력");
			System.out.println("(2) 출력");
			System.out.println("(3) 종료");
			System.out.println("--------------");

			int s = in.nextInt();

			if (s == 1) {
				in1 = new Info();
				System.out.print("이름 입력 : ");
				in1.name = in.next();
				System.out.print("번호 입력 : ");
				in1.number = in.nextInt();
				list.add(in1);
				count++;

			} else if (s ==2) {
				for (int i = 0; i < count; i++) {
					System.out.println("이름 : " + list.get(i).name);
					System.out.println("번호 : " + list.get(i).number);
				}
				
				
			}else if (s== 3) {
				System.out.println("종료");
				break;
			}

		}
	}
}

1하나 할때마다 new Info();방이 생겨서 저장가능

그래서 꼭 if문안에 넣어줘야함

 

 

 

 

 

 

 

package com.chap01;

import java.util.ArrayList;
import java.util.Scanner;

public class Ex05 {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		ArrayList<Info> list = new ArrayList<Info>();
		Info in1 ;
	//	int count = 0;
		
		for(;;) {
			System.out.println("-----MENU-----");
			System.out.println("(1) 입력");
			System.out.println("(2) 출력");
			System.out.println("(3) 종료");
			System.out.println("--------------");

			int s = in.nextInt();

			if (s == 1) {
				in1 = new Info();
				System.out.print("이름 입력 : ");
				in1.name = in.next();
				System.out.print("번호 입력 : ");
				in1.number = in.nextInt();
				list.add(in1);
				//count++;

			} else if (s ==2) {
				for (int i = 0; i < list.size(); i++) {
					System.out.println("이름 : " + list.get(i).name);
					System.out.println("번호 : " + list.get(i).number);
				}
				
				
			}else if (s== 3) {
				System.out.println("종료");
				break;
			}

		}
	}
}

카운트변수안쓰고 하는법

 

 

 

 

 

 

 

 

• map

package com.chap01;
import java.util.*;
public class HashMapExample {

	public static void main(String[] args) {
		//Map컬렉션 생성
		Map<String, Integer> map = new HashMap<String, Integer>();
		
		//객체 저장
		map.put("아현이", 85);
		map.put("윤지양", 80);
		map.put("서우씨", 95);
		System.out.println("총 Entry 수 : " + map.size());
		
		//객체를 하나씩 처리
		Set<String> keySet = map.keySet();
		Iterator<String> keyIterator = keySet.iterator();
		while (keyIterator.hasNext()) {
			String key = keyIterator.next();
			Integer value = map.get(key);
			System.out.println(key + ":" + value);
		}
	}

}

총 Entry 수 : 3
윤지양:80
서우씨:95
아현이:85

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• 상속

package com.chap02;

class People {
	public String name;
	public String ssn;
	public int studenNo;
	
	public People(String name, String ssn, int studentNo) {
		this.name = name;
		this.ssn = ssn;
		this.studenNo = studentNo;
	}
}

class Student extends People{

	public Student(String name, String ssn, int studentNo) {
		super(name, ssn, studentNo);
	}
	
}
public class StudentExample {

	public static void main(String[] args) {
		Student student = new Student("홍길동", "123456-1234567", 1);
		System.out.println("name : " + student.name);
		System.out.println("ssn :" + student.ssn);
		System.out.println("studentNo : " + student.studenNo);
	}
}

super사용하기

 

 

 

package com.chap02;

class People {
	public String name;
	public String ssn;
	
	public People(String name, String ssn, int studentNo) {
		this.name = name;
		this.ssn = ssn;
	}
}

class Student extends People{
	public int studenNo;

	public Student(String name, String ssn, int studentNo) {
		super(name, ssn, studentNo);
		this.studenNo = studentNo;
	}
	
}
public class StudentExample {

	public static void main(String[] args) {
		Student student = new Student("홍길동", "123456-1234567", 1);
		System.out.println("name : " + student.name);
		System.out.println("ssn :" + student.ssn);
		System.out.println("studentNo : " + student.studenNo);
	}
}

쌤은 이렇게 하셧당

 

본인꺼불러올때는 this 부모꺼 불러올때는 super

 

 

 

final써서 stop오버라이딩 못함