포스코 2023-10-25

OOP 실습

/* 클래스 */
public class Animal {
  ...
}
/* 객체와 인스턴스 */
public class Main {
  public static void main(String[] args) {
    Animal cat, dog; // '객체'

    // 인스턴스화
    cat = new Animal(); // cat은 Animal 클래스의 '인스턴스'(객체를 메모리에 할당)
    dog = new Animal(); // dog은 Animal 클래스의 '인스턴스'(객체를 메모리에 할당)
  }
}
https://gmlwjd9405.github.io/2018/09/17/class-object-instance.html

```java
package timetest;

import java.util.Scanner;

public class timetest {
	public static void main(String[] args) {
		 Scanner sc = new Scanner(System.in);
		 System.out.print("시/분/초 입력: ");
		 int hour = sc.nextInt();
		 int min = sc.nextInt();
		 int sec = sc.nextInt();
		 time first_time = new time(10, 10, 10);
		 time second_time = new time(hour, min, sec);
		 time add_time = first_time.add(second_time); // add 메소드 호출
		 
		 System.out.println("두 시간의 합은");
		 add_time.print_time( ); // print_time 메소드 호출
		 time sub_time = first_time.sub(second_time); // sub 메소드 호출
		 System.out.println("두 시간의 차는");
		 sub_time.print_time( ); // print_time 메소드 호출
		 int result = first_time.compare(second_time); // compare 메소드 호출
		 System.out.println(result); // compare 결과 출력
	}
	
	public static class time {
		static int day = 0;
		int hour;
		int min;
		int sec;
		int max = 24 * 60 * 60;
		
		public time() {
			this.hour = 0;
			this.min = 0;
			this.sec = 0;
		}
		
		public time(int hour, int min, int sec) {
			this.hour = hour;
			this.min = min;
			this.sec = sec;
		}
		
		public int compare(time time) {
			int a = convert(this.hour, this.min, this.sec);
			int b = convert(time.hour, time.min, time.sec);
			
			if (a > b) {
				return 1;
			}
			
			else if (a == b) {
				return 0;
			}
			
			else {
				return -1;
			}
		}
		
		public int convert(int hour, int min, int sec) {
			int result;
			result = hour * 3600 + min * 60 + sec;
			return result;
		}
		
		public time add(time time) {
			int addingTime = convert(time.hour, time.min, time.sec);
			int curTime = convert(this.hour, this.min, this.sec);
			int result = addingTime + curTime;
			
			if (result >= time.max) {
				day = 1;
				result = result - time.max;
				int cur_hour = (int) Math.ceil(result / 3600);
				int remain = result % 3600;
				
				time time_add = new time(cur_hour, (int) Math.ceil(remain / 60), remain % 60);
				return time_add;
			}
			
			else {
				day = 0;
				int cur_hour = (int) Math.ceil(result / 3600);
				int remain = result % 3600;
				hour = cur_hour;
				min = (int) Math.ceil(remain / 60);
				sec = remain % 60;
				
				time time_add = new time(cur_hour, (int) Math.ceil(remain / 60), remain % 60);
				return time_add;
			}
			
		}
		
		public time sub(time time) {
			
			int addingTime = convert(time.hour, time.min, time.sec);
			int curTime = convert(this.hour, this.min, this.sec);
			
			int result = curTime - addingTime;
			
			if (result < 0) {
				day = -1;
				result = result + time.max;
				int cur_hour = (int) Math.ceil(result / 3600);
				int remain = result % 3600;
				hour = cur_hour;
				min = (int) Math.ceil(remain / 60);
				sec = remain % 60;
			}
			
			else {
				day = 0;
				int cur_hour = (int) Math.ceil(result / 3600);
				int remain = result % 3600;
				hour = cur_hour;
				min = (int) Math.ceil(remain / 60);
				sec = remain % 60;
			}
			time time_sub = new time(hour, min, sec);
			return time_sub;
			
		}
		
		public void print_time() {
			if (this.day >= 1) {
				System.out.println("후일 " + this.hour + "시 " + this.min + "분 " + this.sec + "초 " + "입니다");
			}
			
			else if (this.day == 0) {
				System.out.println("당일 " + this.hour + "시 " + this.min + "분 " + this.sec + "초 " + "입니다");
			}
			
			else {
				System.out.println("전일 " + this.hour + "시 " + this.min + "분 " + this.sec + "초 " + "입니다");
			}
		}
	}
}

클래스 만들어봄
그 this로 하면 값 계속 변하는거 조심
class안에 class 2개 만들수 있음

package secondPractice;

import java.util.Scanner;

public class secondPractice {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		String s = sc.nextLine();
		String t = sc.nextLine();
		
		Tr P = new Select(s,t);
		Tr Q = ((Select)P).check();
		System.out.println(((Select)P).connect(Q));
		
	}
	
	public static class Tr {
		public String s;
		public String t;
		
		public Tr() {}
		
		public Tr(String s, String t) {
			this.s = s;
			this.t = t;
		}
	}

	public static class Strcmp extends Tr {
		public Strcmp(String s, String t) {
			super(s, t);
		}
		
		public int cmp() {
			return this.s.compareTo(this.t);
		}
	}
	
	public static class Numcmp extends Tr {
		double a, b; int result;
		
		public Numcmp(String s, String t) {
			super(s, t);
		}

		public int cmp() {
			a = Double.parseDouble(this.s);
			b = Double.parseDouble(this.t);
			if (a > b) result = 1;
			else if (a < b) result = -1;
			else result = 0;
			return result;
		}
	}
	
	public static class Select extends Tr {

		public Select(String s, String t) {
			super(s, t);
		}
		
		public Tr check () {
			char neg_sign = '-';
			char s_first_val = this.s.charAt(0);
			char t_first_val = this.t.charAt(0);
			int i = 0;
			int j = 0;
			
			if (s_first_val == neg_sign) {
				i = 1;
			}
			
			if (t_first_val == neg_sign) {
				j = 1;
			}
			
			for (int k = i; k < this.s.length(); k++) {
				char val = this.s.charAt(i);
				char point = '.';
				
				if ((val == point) | (Character.isDigit(val))) {
					continue;
				}
				
				else {
					return new Strcmp(this.s, this.t);
				}
			}
			
			for (int x = j; x < this.t.length(); x++) {
				char val = this.t.charAt(x);
				char point = '.';
				
				if ((val == point) | (Character.isDigit(val))) {
					continue;
				}
				
				else {
					return new Strcmp(this.s, this.t);
				}
			}
			
			return new Numcmp(this.s, this.t);
		}
		
		public int connect(Tr tr) {
			if (tr instanceof Numcmp) {
				Numcmp num = new Numcmp(s, t);
				return num.cmp();
			} else {
				Strcmp str = new Strcmp(s, t);
				return str.cmp();
			}
		}
	}
}

자바는 너무 바보다.
객체지향은 누가 만들었을까.
자바를 하기 싫다.
근데 해야된다.
이걸 어떡하냐.