The relationship between inputstream outputstream and byte[]

1. Data source

InputStream is essentially byte[], input means that data is obtained from the outside to memory and encapsulated in byte[].

Subclasses:
FileInputStream is to obtain data from files (files, data not in memory);
ByteArrayInputStream obtains data from memory (data that already exists in memory);
eventually, an Object of InputStream type is generated.

2. Code Analysis

2.1 Simply copy files

    public static void main(String[] args) throws IOException {
    
    

        InputStream inputStream = new FileInputStream("D:\\DAY_WORK\\2020\\month_10\\10_月.txt");
        OutputStream outputStream = new FileOutputStream("D:\\DAY_WORK\\2020\\month_10\\10_copy.txt");
        byte[] bytes = new byte[inputStream.available()];

        inputStream.read(bytes);
        outputStream.write(bytes);

        inputStream.close();
        outputStream.close();
    }

2.2 Copy files in units of 1024

    public static void main(String[] args) throws IOException {
    
    

        InputStream inputStream = new FileInputStream("D:\\DAY_WORK\\2020\\month_10\\My Favorite 修改说明.docx");
        OutputStream outputStream = new FileOutputStream("D:\\DAY_WORK\\2020\\month_10\\My Favorite 修改说明copy.docx");

        byte[] bytes = new byte[1024];
        int n;
        final int end = -1;
        while (end != (n = inputStream.read(bytes))) {
    
    
            outputStream.write(bytes, 0, n);
        }

        inputStream.close();
        outputStream.close();
    }

2.3 Add a sentence to the content of the file

    public static void main(String[] args) throws IOException {
    
    

        OutputStream outputStream = new FileOutputStream("D:\\DAY_WORK\\2020\\month_10\\10_copy.txt", true);

        String content = "\n今天又是 nice 的一天";
        byte[] bytes = content.getBytes();

        outputStream.write(bytes);
        outputStream.close();
    }

3. The difference between outputstream and Writer/FileWriter

The unit of outPutStream is byte; the unit of
Writer/FileWriter is character, which has encoding problems.