Filewriter/ FileReader ->문자단위일 경우

1)

package bookpractice0410;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Scanner;

public class FileTest {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int num = 1;
		try (FileWriter f = new FileWriter("짱구의 일기.txt")) {
			while (num == 1) {
				System.out.print("문자열입력");
				String st = sc.nextLine();
				f.write(st + "\n");
				System.out.println("1.계속 0 그만");
				num = sc.nextInt();
				st = sc.nextLine();
			}
		} catch (IOException e) {
			e.printStackTrace();
		}

		try(FileReader r = new FileReader("짱구의 일기.txt")) {
			char[] buff = new char[100];
			r.read(buff);
			for (int i = 0; i < buff.length; i++) {
				System.out.print(buff[i]);
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}

		
		
		
	}
}

2)나혼자 연습

package bookpractice0410;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;

public class FilePracticeMyself {

	public static void main(String[] args) {
		try (FileWriter f = new FileWriter("ting.txt")){
			f.write("흥행흥행1" +"\n");
			f.write("흥행흥행2" +"\n");
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		
		try (FileReader rr = new FileReader("ting.txt")){
			ArrayList<Character> ac = new ArrayList<>();
			int a;
			while((a=rr.read()) !=-1) {
				ac.add((char)a);
			}
			for(int i=0; i<ac.size(); i++) {
				System.out.print(ac.get(i));
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e1) {
			e1.printStackTrace();
		}
		
		

	}
}

3)스캐너로 입력

package bookpractice0410;

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;

class Diary {
	int num;
	String date;

	public int getNum() {
		return num;
	}

	public void setNum(int num) {
		this.num = num;
	}

	public String getDate() {
		return date;
	}

	public void setDate(String date) {
		this.date = date;
	}

}

public class fileTest2 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		Diary d = new Diary();
		
		while (true) {
			System.out.print("1.일기쓰기 2.일기보기 0.종료");
			int num = sc.nextInt();
			sc.nextLine();
			if (num == 1) {
				System.out.print("일기제목은?");
				String name = sc.nextLine();
				try (FileWriter f = new FileWriter(name + ".txt")) {
					System.out.println("내용입력하세요");
					while (true) {
						f.write(name + "\n");
						name = sc.nextLine();
						if (name.equals("짱구")) {
							break;
						}
					}
				} catch (IOException e) {
					e.printStackTrace();
				}
			} else if (num == 2) {
				System.out.print("조회할 파일명 입력");
				String name = sc.nextLine();
				try (FileReader r = new FileReader(name + ".txt")){
					ArrayList<Character> ac = new ArrayList<>();
					int c;
					while((c=r.read()) !=-1 ) {
						ac.add((char)c);
					}
					for(Character a : ac) {
						System.out.print(a);
					}
				} catch (FileNotFoundException e) {
					e.printStackTrace();
				} catch (IOException e1) {
					e1.printStackTrace();
				}
			} else if (num == 0) {
				System.out.println("종료한다 오버");
				break;
			}
		}
	}

}