I/o basic knowledge sorting

I/O The following function types are involved in the stream

The readout is divided into the following 5 Kind of ：
FileReader Read file contents （ Convert the file into a character stream to read , It reads char Array or String ）
BufferReader packing FileReader Generate buffer More efficient
InputStream It's an interface ( You can't new InputStream);
FileInputStream Read file contents （ Byte stream read , binary data , It reads byte Array .）
InputStreamReader Stream bytes into character streams

Writing is divided into corresponding 5 Kind of ：
FileWriter
BufferedWriter
OutputStream
FileOutputStream
OutputStreamWriter
Be sure to distinguish which is written , Which one is read
read out ：
FileInputStream
FileReader
write in ：
FileOutputStream
FileWriter
Don't talk much , Go straight to the example （ Copy code directly try catch that will do ）

1. Read file contents

FileReader Read

 File file = new File(" File pathname ");
        // Read file related functions 
        FileReader fileReader = null;
       fileReader = new FileReader("file");
        char c = 0;
        do {
            c=(char)fileReader.read();// Read a character 
            System.out.println(c);
        }while (c != '-1');
    fileReader.close();

BufferReader and FileReader Combined reading

 File file = new File(" File path ");
  BufferedReader bufferedReader=null;
       bufferedReader = new BufferedReader(new FileReader(file));
        String s;
        while((s=bufferedReader.readLine()) != null){
            System.out.println(s);
        }
        bufferedReader.close();
        //bufferedReader stay close Will automatically put FileReader to close fall 

InputStreamReader new come out FileInputStream Read
Mode one

File file = new File(" File path ");
 InputStreamReader inputStreamReader = null;
       inputStreamReader = new InputStreamReader(new FileInputStream(file),"UTF-8");
        char[] ch=new char[2014];
		        int len=inputStreamReader.read(ch);
		        System.out.println(new String(ch,0,len));
		        inputStreamReader.close();
		        

The parameter in the method needs to be passed a byte Type array .
Mode two

File file = new File(" File path ");
		InputStreamReader inputStreamReader = null;
		try {
			inputStreamReader = new InputStreamReader(new FileInputStream(file));
			 StringBuffer stringBuffer = new StringBuffer();
			 while(inputStreamReader.ready()) {
				 stringBuffer.append((char)inputStreamReader.read());
			 }
			 System.out.println(stringBuffer.toString());
		        inputStreamReader.close();
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		}
	}

Read what you type from the keyboard

BufferReader and InputStreamReader A mixture of

According to the line read

BufferedReader bufferedReader  = null;
bufferedReader  = new BufferedReader(new InputStreamReader(System.in));
        System.out.println(" When the input “ sign out ” Exit input when ：");
        String s = "";
        do {
            s = bufferedReader.readline();
            System.out.println(s);
        }while (c!=" sign out ");
         bufferedReader.close();

Read by character

BufferedReader bufferedReader = null;
bufferedReader  = new BufferedReader(new InputStreamReader(System.in));
        System.out.println(" When the input ‘q’ Exit input when ：");
        char c;
        do {
            c = (char) bufferedReader.read();
            System.out.println(c);
        }while (c!='q');
                bufferedReader.close();

2. Write file contents

FileWriter write in

File file = new File(" File path ");
FileWriter fileWriter = null;
        fileWriter = new FileWriter(file);
        fileWriter.append(" Insert content ");
        fileWriter.close();

BufferedWriter and FileWriter Combined write

File file = new File(" File path ");
BufferedWriter bufferedWriter = null;
      bufferedWriter = new BufferedWriter(new FileWriter(file));
        bufferedWriter.write(" Insert content ");
        bufferedWriter.close();

OutputStreamWriter new come out FileOutputStream write in
If FileOutputStream If the object file does not exist, the file will be created automatically

File file = new File(" File path ");
FileOutputStream fileOutputStream = new FileOutputStream("file ");
        OutputStreamWriter outputStreamWriter = null;
       outputStreamWriter = new OutputStreamWriter(fileOutputStream,"UTF-8");
        outputStreamWriter.append(" Insert content ");
        outputStreamWriter.append("\r\n");// Line break 
        outputStreamWriter.close();
        fileOutputStream.close();

Using interfaces OutputStream new come out FileOutputStream Write with other files
（ Other documents here refer to Excel Form file ）

  OutputStream outputStream = null;
        try {
            outputStream = new FileOutputStream("workbook.xlsx");
            Workbook workbook = new XSSFWorkbook();
            Sheet sheet = workbook.createSheet("firstSheet");
            Row row = sheet.createRow(0);
            row.createCell(0).setCellValue(1);
            workbook.write(outputStream);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if (outputStream != null){
                try {
                    outputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

Use WorkBook Of write() The parameters in the method must be OutputStream