Five ways to create and write files in Java IO

Java IO 5 ways to create and write files

Files.new BufferedWriter (Java 8)
Files.writer (Java 7 recommended)
PrintWriter
File.createNewFile
FileOutputStream.writer(byte[] b) pipe stream

Files.new BufferedWriter

public class testCreateFile1 {
    
    
    @Test
    public void test1() throws IOException {
    
    
        String fileName = "C:\\Users\\DELL\\Desktop\\test\\ceshi.txt";
        Path path = Paths.get(fileName);
        //使用newBufferedWriter创建文件并写文件
        //使用try-with-resource方法关闭流，不用手动关闭
        try (BufferedWriter writer = Files.newBufferedWriter(path, StandardCharsets.UTF_8)) {
    
    
            writer.write("第二次使用Files.newBufferedWriter创建文件！！！");
        }

        //追加写模式
        try(BufferedWriter writer = Files.newBufferedWriter(path,StandardCharsets.UTF_8, StandardOpenOption.APPEND)){
    
    
            writer.write("使用这种【BufferedWriter writer = Files.newBufferedWriter(path,StandardCharsets.UTF_8, StandardOpenOption.APPEND)】追加模式");
        }
    }
}

Files.writer

@Test
public void test2() throws IOException {
    
    
    String fileName = "C:\\Users\\DELL\\Desktop\\test\\ceshi1.txt";
    Path path = Paths.get(fileName);
    //从jdk7开始提供的方法
    //使用Files.writer创建一个文件并写入
    Files.write(path, "创建文件".getBytes(StandardCharsets.UTF_8));
    //追加写模式【这种模式必须确保文件已存在】
    Files.write(path, "创建文件".getBytes(StandardCharsets.UTF_8), StandardOpenOption.APPEND);
}

PrintWriter

@Test
public void test3() throws FileNotFoundException, UnsupportedEncodingException {
    
    
    String fileName = "C:\\Users\\DELL\\Desktop\\test\\ceshi2.txt";

    //JDK 1.5开始提供的方法
    try (PrintWriter writer = new PrintWriter(fileName, "UTF-8")) {
    
    
        writer.println("创建文件");
    }
}

File.createNewFile

@Test
public void test4() throws IOException {
    
    
    String fileName = "C:\\Users\\DELL\\Desktop\\test\\ceshi3.txt";

    File file = new File(fileName);

    //返回true 表示创建文件成功
    //false 表示文件已经存在
    if (file.createNewFile()) {
    
    
        System.out.println("文件创建成功");
    } else {
    
    
        System.out.println("文件已经存在不需要重复创建");
    }

    // 使用FileWriter写文件
    try (FileWriter writer = new FileWriter(file)) {
    
    
        writer.write("创建文件");
    }
}

FileOutputStream.writer(byte[] b) pipe stream

@Test
public void test5() throws IOException {
    
    
    String fileName = "C:\\Users\\DELL\\Desktop\\test\\ceshi4.txt";
    try (
        FileOutputStream fos = new FileOutputStream(fileName);
        OutputStreamWriter osw = new OutputStreamWriter(fos, "utf-8");
        BufferedWriter bw = new BufferedWriter(osw);
    ) {
    
    
        bw.write("创建文件！！");
    }
}

6 ways to read file data in Java IO

Files.lines returns Stream (Java 8) streaming data processing, reads line by line
Files.readAllLines returns List (Java 8)
Files.readString reads String (Java11) file maximum 2G
Files.readAllBytes reads byte[] (Java 7 ) File maximum 2G
BufferedReader classic way