Character stream

Character output stream (Writer)

Implement the subclass FileWriter
Code example:

public class Demo04 {
    public static void main(String[] args) throws IOException {
        FileWriter fWriter = new FileWriter("/Users/james/Desktop/level/haha.txt");
        fWriter.write(100);
        // Note that the character output stream needs to call the refresh method when writing to the file
        // It is recommended to refresh every write
        fWriter.flush();
        char[] c = {'l','o','n','g'};
        fWriter.write(c);
        fWriter.flush();
        fWriter.write(c, 1,3);
        fWriter.flush();
        // Write directly with string
        fWriter.write("Draw a knife, cut off the water, make the water more flowing\n");
        fWriter.flush();
        fWriter.write("To drink away sorrow is more sorrow\n");
        fWriter.flush();
        fWriter.write("A hundred days on the mountain", 1, 2);
        // Refresh before closing resources
        fWriter.close();
    }
}

Character input stream (Reader)

Implementation subclass: FileReader
Code example:

public class Demo05 {
    public static void main(String[] args) throws IOException {
        FileReader reader = new FileReader("/Users/james/Desktop/level/haha.txt");
        // Circular reading
        char[] bs = new char[1024];
        int len = 0;
        while ((len = reader.read(bs)) != -1) {
            System.out.println(new String(bs, 0, len));
        }
        reader.close();
    }
}

In character stream, string type can be written directly in output stream, but only input stream. Why?

Example contact:

public class Demo06 {
    public static void main(String[] args) {

        File file = new File("/Users/james/Desktop/level/haha.txt");
        File file2 = new File("/Users/james/Desktop/level/ha.txt");
        copyFileTxt(file, file2);

    }

    // Character stream copy file
    public static void copyFileTxt(File src ,File dest) {
        FileReader reader = null;
        FileWriter writer = null;

        try {
            reader = new FileReader(src);
            writer = new FileWriter(dest);
            char[] c = new char[1024];
            int len = 0;
            while ((len = reader.read(c)) != -1) {
                writer.write(c, 0, len);
            }               
        } catch (FileNotFoundException e) {
            throw new RuntimeException("cannot find file");
        } catch (IOException e) {
            throw new RuntimeException("Compile exception");
        }finally {
            try {
                if (reader != null) {
                    reader.close();
                }               
            } catch (IOException e) {
                throw new RuntimeException("Resource close exception");
            }finally {
                try {
                    if (writer != null) {
                        writer.close();
                    }
                } catch (IOException e) {
                    throw new RuntimeException("Resource close exception");
                }
            }
        }
    }
}

Conversion flow

Outputstreamwriter (character stream to byte stream)

Inputstreamreader (byte stream to character stream)

Code example:

public class Demo07 {
    public static void main(String[] args) throws IOException {
        //getUTF8();
//      getGBK();
//      readUTF8();
        readGBK();
    }

    // Write using the default UTF-8 of OutputStreamWriter
    public static void getUTF8() throws IOException {
        FileOutputStream fos = new FileOutputStream("/Users/james/Desktop/level/utf-8.txt");
        // Create conversion stream character stream to byte stream
        OutputStreamWriter osw = new OutputStreamWriter(fos);
        // Write file
        osw.write("Snow in wisdom, rain in Apricot,Under the cherry tree, in the flower field");
        // Close resources (only the outer flow can be closed)
        osw.close();

    }
    // Using the conversion stream to write the file OutputStreamWriter using GBK
    public static void getGBK() throws IOException {
            FileOutputStream fos = new FileOutputStream("/Users/james/Desktop/level/GBK.txt");
        // Build transform stream in encoding format (strings in encoding format ignore case)
        OutputStreamWriter osw = new OutputStreamWriter(fos, "GBK");
        osw.write("Snow in wisdom, rain in Apricot,Under the cherry tree, in the flower field");
        osw.close();    
    }

    public static void readUTF8() throws IOException {
        FileInputStream fis = new FileInputStream("/Users/james/Desktop/level/utf-8.txt");
        InputStreamReader isr = new InputStreamReader(fis); 
        int len = 0;
        char[] b = new char[1024];
        while ((len = isr.read(b)) != -1) {
            System.out.println(new String(b, 0, len));
        }

        isr.close();
    }

    public static void readGBK() throws IOException {
        FileInputStream fis = new FileInputStream("/Users/james/Desktop/level/GBK.txt");
        InputStreamReader isr = new InputStreamReader(fis,"GBK"); 
        int len = 0;
        char[] b = new char[1024];
        while ((len = isr.read(b)) != -1) {
            System.out.println(new String(b, 0, len));
        }
        isr.close();
    }
}