Java 讀寫檔案文字的幾種方法

在這裡我紀錄了一些 Java 讀寫檔案文字內容的一些方法：

package test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;

public class FileReadWriteTest {

	public static void main(String[] args) throws IOException {
		String filePath = "D:\\MyTextFileTest.txt";
		new File(filePath).createNewFile();

		writeFileContent_1(filePath, true, "中文字測試");
		writeFileContent_1(filePath, true, "你好哈囉");
		
		System.out.println(readFileContent_1(filePath));
		System.out.println(readFileContent_2(filePath));
	}
	
	/*************** Write File ***************/
	public static void writeFileContent_1(String filePath, boolean isAppend, String contentToWrite) {		
		try (
				FileOutputStream fileOutputStream = new FileOutputStream(new File(filePath), isAppend);
				OutputStreamWriter outputStreamWriter = new OutputStreamWriter(fileOutputStream, "UTF-8");
				BufferedWriter bufferedWriter = new BufferedWriter(outputStreamWriter);
			){
			
			bufferedWriter.write(contentToWrite);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	public static void writeFileContent_2(String filePath, boolean isAppend, String contentToWrite) {
		try {
			if (isAppend) {			
				Files.writeString(Paths.get(filePath), contentToWrite, StandardCharsets.UTF_8, StandardOpenOption.APPEND);			
			}else {
				Files.writeString(Paths.get(filePath), contentToWrite, StandardCharsets.UTF_8);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		
	}
	
	/*************** Read File ***************/
	public static String readFileContent_1(String filePath) {
		StringBuffer fileContent = new StringBuffer();

		try (
				FileInputStream fileInputStream = new FileInputStream(new File(filePath));
				InputStreamReader inputStreamReader = new InputStreamReader(fileInputStream, "UTF-8");
				BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
			) {
			
			String readContent = "";
			while ((readContent = bufferedReader.readLine()) != null) {
				fileContent.append(readContent + "\n");
			}
			if (fileContent.length() > 0) {
				//remove the latest added "\n"
				fileContent.deleteCharAt(fileContent.length() - 1);
			}
		} catch (IOException e) {
			e.printStackTrace();
		}

		return fileContent.toString();
	}
	
	public static String readFileContent_2(String filePath) {
		String fileContent = "";
		
		try {
			fileContent = Files.readString(Paths.get(filePath), StandardCharsets.UTF_8);
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		return fileContent;
	}
}

參考資料：

1. How to read UTF-8 encoded data from a file – Java
2. How to append text to an existing file in Java?