Java Fundamentals Hardening IO Stream Note 59: Print Stream

1. Print Flow

(1) Classification:

• Byte print stream PrintStream

　　• character print stream PrintWriter

(2) Characteristics of the print flow:

• can only write data , cannot read data

• Only the destination can be manipulated and the data source cannot be manipulated

　　• can manipulate any type of data

　　• automatically refresh if automatic refresh is enabled

　　• the ability to manipulate text files directly

(3) Attachment problem: which objects can directly manipulate the text file?

• FileInputStream
• FileOutputStream
• FileReader
• FileWriter
• PrintStream
• PrintWriter

2. PrintWriter of the print stream (character print stream):

(1)PrintWriter Basic use:

1  Packagecn.itcast_03;2 3 Importjava.io.IOException;4 ImportJava.io.PrintWriter;5 6  Public classPrintwriterdemo {7      Public Static voidMain (string[] args)throwsIOException {8         //use as a subclass of writer9PrintWriter PW =NewPrintWriter ("Pw.txt");Ten  OnePw.write ("Hello"); APw.write ("World"); -Pw.write ("Java"); -          the pw.close (); -     } -}

The results are as follows:

(2) PrintWriter operation of any type of data:

The code is as follows:

1  Packagecn.itcast_03;2 3 ImportJava.io.FileWriter;4 Importjava.io.IOException;5 ImportJava.io.PrintWriter;6 7 /*8 * 1: Any type of data can be manipulated. 9 * PRINT ()Ten * println () One * 2: Start auto Refresh A * PrintWriter pw = new PrintWriter (New FileWriter ("Pw2.txt"), true); - * or you should call the println () method to  - * This time not only automatically refreshed , but also to achieve the data line-breaking .  the  *  - * println ()  - * actually equivalent to : - * bw.write ();  + * bw.newline ();  - * Bw.flush ();  +  */ A  Public classPrintWriterDemo2 { at      Public Static voidMain (string[] args)throwsIOException { -         //Create a Print flow object -         //PrintWriter pw = new PrintWriter ("Pw2.txt"); -PrintWriter PW =NewPrintWriter (NewFileWriter ("Pw2.txt"),true); -  -         //write () is uncertain, how to do ? in         //we should see a new way of it. -         //Pw.print (true); to         //Pw.print (+); +         //pw.print ("Hello"); -  thePw.println ("Hello"); *Pw.println (true); $PW.PRINTLN (100);Panax Notoginseng  - pw.close (); the     } +}

Run the effect as follows:

Java Fundamentals Hardening IO Stream Note 59: Print stream