FileReader

	public static void m1() {
		File file = new File("c:\\storage", "m2.txt");
		FileReader fr = null;
		try {
        	fr = new FileReader(file);
            // File 입력 데이터
			// 1. 1글자 : int
			// 2. 여러글자 : char[]
			// 1글자를 저장할 변수
			int c;
			// read() 메소드
			// 1. 읽은 문자를 반환
			// 2. 모두 읽어서 읽은 문자가 없으면 -1 반환
			// String str에 파일 내용 저장하기
			StringBuilder sb = new StringBuilder();
			while((c = fr.read()) != -1) {
				sb.append((char)c);
			}	
			String str = sb.toString();
			System.out.println(str);
			} catch (IOException e) {
				e.printStackTrace();
			} finally {
				try {
					if(fr != null) {
						fr.close();
					}
				} catch (IOException e) {
					e.printStackTrace();
				}
		} 
	}

FileReader

	public static void m2() {
		File file = new File("c:\\storage", "m3.txt");
		FileReader fr = null;
		try {
			fr = new FileReader(file);
			// 3글자를 저장할 배열
			char[] cbuf = new char[5];
			// read(char[] cbuf) 메소드
			// 1. 읽은 글자는 cbuf 배열에 저장
			// 2. 실제로 읽은 글자 수를 반환
			// 3. 읽은 글자가 없으면 -1 반환
			// m3.txt 파일 읽는 과정
			//     readCnt      cbuf
			// 1     5          a   p   p   l   e
			// 2     5          \n  m   a   n   g
			// 3     2          o   \n  a   n   g
			// 4    -1
			while(true) {
				int readCnt = fr.read(cbuf);
				if(readCnt == -1) {
					break;
				}
				for(int i = 0; i < readCnt; i++) { // 읽은 글자 수(readCnt)만큼 반복
					System.out.print(cbuf[i]);
				}
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
			if(fr != null) {
				fr.close();
			}
			} catch (IOException e) {
				e.printStackTrace();
		}
		}
	}

m3.txt 읽어서 String str에 저장

		File file = new File("C:\\storage", "m3.txt");
		FileReader fr = null;
		try {
			fr = new FileReader(file);
			char[] cbuf = new char[5];
			StringBuilder sb = new StringBuilder();
			int readCnt;
			while((readCnt = fr.read(cbuf)) != -1) {
				sb.append(cbuf, 0, readCnt);
			}
			String str = sb.toString();
			System.out.println(str);
		} catch(IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if(fr != null) {
					fr.close();
				}
		} catch(IOException e) {
			e.printStackTrace();
		}
	}
}

BufferedReader

		File file = new File("C:\\storage", "m4.txt");
		FileReader fr = null;
		BufferedReader br = null;
		try {
			fr = new FileReader(file);
			br = new BufferedReader(fr);
			StringBuilder sb = new StringBuilder();
			String line = null;
			while((line = br.readLine()) != null) {
				sb.append(line + "\n");
			}
			String str = sb.toString();
			System.out.println(str);
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if(br != null) {
					br.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

try-catch-resources문

		try (BufferedReader br = new BufferedReader(new FileReader("c:\\storage\\m3.txt"))) {
			StringBuilder sb = new StringBuilder();
			String line = null;
			while((line = br.readLine()) != null) {
				sb.append(line + "\n");
			}
			String str = sb.toString();
			System.out.println(str);
		} catch (IOException e) {
			e.printStackTrace();
		}

CSVReader

• Product 클래스

public class Product {
	private String number;
	private String name;
	private int price;
	public Product() {
	}
	public Product(String number, String name, int price) {
		super();
		this.number = number;
		this.name = name;
		this.price = price;
	}
	public String getNumber() {
		return number;
	}
	public void setNumber(String number) {
		this.number = number;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getPrice() {
		return price;
	}
	public void setPrice(int price) {
		this.price = price;
	}
	@Override
	public String toString() {
		return "Product [number=" + number + ", name=" + name + ", price=" + price + "]";
	}

• CSVReader 클래스

	public static void main(String[] args) {
		File file = new File("c:\\storage", "product.csv");
		try(BufferedReader br = new BufferedReader(new FileReader(file))) {
			// 첫 행 읽어 버리기
			br.readLine();
			// 한 줄 읽어서 Product 객체 생성하고 ArrayList에 저장
			List<Product> products = new ArrayList<Product>();
			String line = null;
			while((line = br.readLine()) != null) {
				String[] arr = line.split(",");
				Product product = new Product();
				product.setNumber(arr[0]);
				product.setName(arr[1]);
				product.setPrice(Integer.parseInt(arr[2]));
				products.add(product);
			}
			// ArrayList 확인
			for(Product product : products) {
				System.out.println(product);
            }
		} catch(IOException e) {
			e.printStackTrace();
		}
	}
}

출력:
Product [number=100, name=새우깡, price=1500]
Product [number=101, name=양파링, price=2000]
Product [number=102, name=홈런볼, price=3000]

XMLReader

• Product 클래스

public class Product {
	private String number;
	private String name;
	private int price;
	public Product() {
	}
	public Product(String number, String name, int price) {
		super();
		this.number = number;
		this.name = name;
		this.price = price;
	}
	public String getNumber() {
		return number;
	}
	public void setNumber(String number) {
		this.number = number;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public int getPrice() {
		return price;
	}
	public void setPrice(int price) {
		this.price = price;
	}
	@Override
	public String toString() {
		return "Product [number=" + number + ", name=" + name + ", price=" + price + "]";
	}
}

• XMLReader클래스

public class XMLReader {
	public static void main(String[] args) {
		try {
			DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
			DocumentBuilder builder = factory.newDocumentBuilder();
			File file = new File("C:\\storage", "product.xml");
			Document document = builder.parse(file); // product.xml을 파싱(분석)한 document 객체
			// 최상위 요소(root)
			Element root = document.getDocumentElement();
			System.out.println("최상위 요소 : " + root.getNodeName());
			// 최상위 요소의 자식 노드들
			NodeList nodeList = root.getChildNodes();
			for(int i = 0; i < nodeList.getLength(); i++) {
				Node node = nodeList.item(i);  // 줄 바꾼(#text)과 <product>태그로 구성
				if(node.getNodeType() == Node.ELEMENT_NODE) { // 노드가 Element인가?(줄바꿈 #text 제외되고 <product>태그만 남음) 
					NodeList nodeList2 = node.getChildNodes(); // <product> 태그의 자식노드(줄바꿈 #text, <number>, <name>, <price> 태그)
					for(int j = 0; j < nodeList2.getLength(); j++) {
						Node node2 = nodeList2.item(j);
						if(node2.getNodeType() == Node.ELEMENT_NODE) {
							System.out.println(node2.getNodeName() + node2.getTextContent());
						}
					}
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

JSONReader

		File file = new File("C:\\storage", "product.json");
		try (BufferedReader br = new BufferedReader(new FileReader(file))) {
			StringBuilder sb = new StringBuilder();
			String line = null;
			while((line = br.readLine()) != null) {
				sb.append(line);
			}
			String str = sb.toString();
			JSONArray arr = new JSONArray(str);
			List<Product> products = new ArrayList<Product>();
			for(int i = 0, length = arr.length(); i < length; i++) {
				JSONObject obj = arr.getJSONObject(i);
				Product product = new Product();
				product.setNumber(obj.getString("number"));
				product.setName(obj.getString("name"));
product.setPrice(Integer.parseInt(obj.getString("price")));
			}
			for(Product product : products) {
				System.out.println(product);
			}
		} catch(IOException e) {
			e.printStackTrace();
		}