Java PrintWriter class

In this tutorial, we will learn about Java PrintWriter and its print() and printf() methods through examples.

The PrintWriter class in the java.io package can be used to write output data in a readable form (text).

It inherits the abstract class Writer.

How PrintWriter works

autoFlush is an optional boolean parameter that specifies whether to perform automatic flushing: The PrintWriter class also has an automatic flushing feature. This means that if one of the println() or printf() methods is called, it will force the writer to write all data to the target.

Create a PrintWriter

To create a print writer, we must import the java.io.PrintWriter package. After importing the package, we can create a print writer.

1.Use other writers

//Create FileWriter
FileWriter file = new FileWriter("output.txt");
//.Using the filename
PrintWriter output = new PrintWriter(file, autoFlush);

);

• We created a print writer that writes data to a FileWriter

• autoFlush is an optional parameter used to specify whether to perform automatic refresh

2.Use other output streams

//　Creates a FileOutputStream
FileOutputStream file = new FileOutputStream("output.txt");
//　Creates a PrintWriter
PrintWriter output = new PrintWriter(file, autoFlush);

);

• We created a print writer that writes data to a file represented by FileWriter

• autoFlush is an optional parameter used to specify whether to perform automatic flushing

3.使用文件名

//.Using the filename
Create PrintWriter

);

• PrintWriter output = new PrintWriter(String file, boolean autoFlush);

• We have created a printer writer that writes data to the specified file

autoFlush is an optional boolean parameter that specifies whether to perform automatic flushingNoteor8In all the above cases, PrintWriter writes data to the file using certain default character encodings. However, we can also specify the character encoding (or16UTF

//)
Create a PrintWriter using certain character encoding

PrintWriter output = new PrintWriter(String file, boolean autoFlush, Charset cs); Here, we usedCharacter set

Class specifying character encoding.

PrintWriter methods

The PrintWriter class provides various methods that allow us to print data to the output.

• print() method - print();

• Print the specified data to the writer - println();

import java.io.PrintWriter;
class Main {
　　public static void main(String[] args) {
　　　　Print the data along with a newline character to the writer
　　　　try {
　　　　　　PrintWriter output = new PrintWriter("output.txt");
　　　　　　String data = "This is a text inside the file.";
　　　　　　output.close();
　　　　}
　　　　catch(Exception e) {
　　　　　　e.getStackTrace();
　　　　}
　　}
}

output.print(data);output.txt.

PrintWriter output = new PrintWriter("output.txt");

In the above example, we created a printer writer named output. This printer writer is linked to the file

Here, when we run the program,output.txtThe file will be filled with the following content.

To print data to the file, we used the print() method.

This is a text inside the file.

printf() method2The printf() method can be used to print formatted strings. It contains

A parameter: the formatted string and the parameters. For example,　25printf("I %d years old",

);

• Here,

• I am %d years old is a formatted string

• 25 %d is the integer data in the formatted string

It is a parameter

Therefore, the formatted string includes text and data. Moreover, the parameters replace the data in the formatted string.％dReplace with25.

Example: Using the PrintWriter's printf() method

import java.io.PrintWriter;
class Main {
　　public static void main(String[] args) {
　　　　try {
　　　　　　PrintWriter output = new PrintWriter("output.txt");
　　　　　　int age =　25;
　　　　　　output.printf("I am %d years old.", age);
　　　　　　output.close();
　　　　}
　　　　catch(Exception e) {
　　　　　　e.getStackTrace();
　　　　}
　　}
}

In the above example, we created a printer writer named output. The printer writer is linked to the file output.txt.

PrintWriter output = new PrintWriter("output.txt");

To print formatted text to the file, we use the printf() method.

Here, when we run the program,output.txtThe file will be filled with the following content.

I am　25　years old.

Other Methods of PrintWriter