Java PrintStream Class

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PrintStream from the java.io package offers useful methods for writing data to the console and files as well as output streams. This class manages data flushing automatically while preventing IOExceptions from occurring but provides error status checks through .checkError().

Syntax:

import java.io.PrintStream;

Creating a PrintStream Object

From System.out (Console Output)

PrintStream ps = System.out;
ps.println("Hello from PrintStream!");

From a File Output Stream

import java.io.*;
PrintStream ps = new PrintStream(new FileOutputStream("output.txt"));
ps.println("This will be written to a file.");
ps.close();  // Always close to flush and free resources

Methods of PrintStream

Method Description
print() Prints without a newline
println() Prints with a newline
printf() Prints formatted text (like C's printf)
write() Writes raw bytes
append() Appends characters or sequences
checkError() Returns true if any error has occurred
close() Closes the stream

Example:

 import java.io.PrintStream;

public class PrintStreamDemo {
    public static void main(String[] args) {
        PrintStream ps = System.out;

        ps.print("Hello, ");
        ps.println("World!");
        ps.printf("Number: %d, Decimal: %.2f", 10, 3.14159);
    }
}

Output

Hello, World!
Number: 10, Decimal: 3.14

Example:

Writing to a File

import java.io.FileNotFoundException;
import java.io.PrintStream;

public class FilePrintStreamExample {
    public static void main(String[] args) {
        try {
            PrintStream ps = new PrintStream("log.txt");
            ps.println("Logging started...");
            ps.printf("Log ID: %d, Status: %s%n", 101, "SUCCESS");
            ps.close();
        } catch (FileNotFoundException e) {
            System.out.println("Error: " + e.getMessage());
        }
    }
}
  • PrintStream is not synchronized. You can use PrintWriter when you need to perform advanced character writing operations with enhanced control features.
  • System.out serves as a PrintStream object which allows System.out.println() and System.out.print() methods to function within this class.
  • Ensuring data reaches its destination requires calling either flush() or close().
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