文件和byte数组之间相互转换

本是古典何须时尚 2022-05-08 05:44 269阅读 0赞

# 文件和byte数组之间相互转换 #

## 文件转换成byte数组 ##

文件转换成byte数组有两种方式：

### 1. 传统方式 ###

File file = new File("/temp/abc.txt");
    //init array with file length
    byte[] bytesArray = new byte[(int) file.length()];
    
    FileInputStream fis = new FileInputStream(file);
    fis.read(bytesArray); //read file into bytes[]
    fis.close();
    
    return bytesArray;

### 2. NIO方式 ###

String filePath = "/temp/abc.txt";
    
    byte[] bFile = Files.readAllBytes(new File(filePath).toPath());
    //or this
    byte[] bFile = Files.readAllBytes(Paths.get(filePath));

### 完整实例 ###

下面的例子展示了如何把读取的文件内容转换成byte数组，使用了传统的`FileInputStream`和`java.nio`两种方式。

import java.io.File;
    import java.io.FileInputStream;
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Path;
    import java.nio.file.Paths;
    
    /**
     * @author zkzong
     * @date 2017/10/20
     */
    public class FileToArrayOfBytes {
        public static void main(String[] args) {
    
            try {
    
                // convert file to byte[]
                byte[] bFile = readBytesFromFile("test.txt");
    
                //java nio
                //byte[] bFile = Files.readAllBytes(new File("test.txt").toPath());
                //byte[] bFile = Files.readAllBytes(Paths.get("test.txt"));
    
                // save byte[] into a file
                Path path = Paths.get("test2.txt");
                Files.write(path, bFile);
    
                System.out.println("Done");
    
                //Print bytes[]
                for (int i = 0; i < bFile.length; i++) {
                    System.out.print((char) bFile[i]);
                }
    
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    
        private static byte[] readBytesFromFile(String filePath) {
    
            FileInputStream fileInputStream = null;
            byte[] bytesArray = null;
    
            try {
    
                File file = new File(filePath);
                bytesArray = new byte[(int) file.length()];
    
                //read file into bytes[]
                fileInputStream = new FileInputStream(file);
                fileInputStream.read(bytesArray);
    
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (fileInputStream != null) {
                    try {
                        fileInputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
    
            }
    
            return bytesArray;
    
        }
    }

## byte数组转换成文件 ##

byte数组转换成文件也有两种方式：

### 1. 传统方式 ###

FileOutputStream fos = new FileOutputStream(fileDest);
    fos.write(bytesArray);
    fos.close();

### 2. NIO方式 ###

Path path = Paths.get(fileDest);
    Files.write(path, bytesArray);

### 完整实例 ###

下面的例子展示了如何把读取的文件内容转换成byte数组，并把保存的byte数组转换成一个新的文件，使用了传统的`try-catch`、JDK 7的`try-resources`和`java.nio`两种方式。

import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileOutputStream;
    import java.io.IOException;
    import java.nio.file.Files;
    import java.nio.file.Path;
    import java.nio.file.Paths;
    
    /**
     * @author zkzong
     * @date 2017/10/20
     */
    public class ArrayOfBytesToFile {
        private static final String UPLOAD_FOLDER = "/";
    
        public static void main(String[] args) {
    
            FileInputStream fileInputStream = null;
    
            try {
    
                File file = new File("test.txt");
                byte[] bFile = new byte[(int) file.length()];
    
                //read file into bytes[]
                fileInputStream = new FileInputStream(file);
                fileInputStream.read(bFile);
    
                //save bytes[] into a file
                writeBytesToFile(bFile, UPLOAD_FOLDER + "test1.txt");
                writeBytesToFileClassic(bFile, UPLOAD_FOLDER + "test2.txt");
                writeBytesToFileNio(bFile, UPLOAD_FOLDER + "test3.txt");
    
                System.out.println("Done");
    
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (fileInputStream != null) {
                    try {
                        fileInputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
    
            }
        }
    
        //Classic, < JDK7
        private static void writeBytesToFileClassic(byte[] bFile, String fileDest) {
    
            FileOutputStream fileOuputStream = null;
    
            try {
                fileOuputStream = new FileOutputStream(fileDest);
                fileOuputStream.write(bFile);
    
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (fileOuputStream != null) {
                    try {
                        fileOuputStream.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
    
        }
    
        //Since JDK 7 - try resources
        private static void writeBytesToFile(byte[] bFile, String fileDest) {
    
            try (FileOutputStream fileOuputStream = new FileOutputStream(fileDest)) {
                fileOuputStream.write(bFile);
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    
        //Since JDK 7, NIO
        private static void writeBytesToFileNio(byte[] bFile, String fileDest) {
    
            try {
                Path path = Paths.get(fileDest);
                Files.write(path, bFile);
            } catch (IOException e) {
                e.printStackTrace();
            }
    
        }
    
    }