Java: PrintStream to String?

Question

I have a function that takes an object of a certain type, and a PrintStream to which to print, and outputs a representation of that object. How can I capture this function's output in a String? Specifically, I want to use it as in a toString method.

Answer 1

Use a ByteArrayOutputStream as a buffer:

import java.io.ByteArrayOutputStream;
import java.io.PrintStream;
import java.nio.charset.StandardCharsets;

    final ByteArrayOutputStream baos = new ByteArrayOutputStream();
    final String utf8 = StandardCharsets.UTF_8.name();
    try (PrintStream ps = new PrintStream(baos, true, utf8)) {
        yourFunction(object, ps);
    }
    String data = baos.toString(utf8);

Answer 2

Why don't you use a StringWriter with a PrintWriter?

StringWriter writer = new StringWriter();
PrintWriter out = new PrintWriter(writer);
out.println("Hello World!");
String output = writer.toString();

Answer 3

You can construct a PrintStream with a ByteArrayOutputStream passed into the constructor which you can later use to grab the text written to the PrintStream.

ByteArrayOutputStream os = new ByteArrayOutputStream();
PrintStream ps = new PrintStream(os);
...
String output = os.toString("UTF8");

Answer 4

Maybe this question might help you: Get an OutputStream into a String

Subclass OutputStream and wrap it in PrintStream

Answer 5

A unification of previous answers, this answer works with Java 1.7 and after. Also, I added code to close the Streams.

final Charset charset = StandardCharsets.UTF_8;
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PrintStream ps = new PrintStream(baos, true, charset.name());
yourFunction(object, ps);
String content = new String(baos.toByteArray(), charset);
ps.close();
baos.close();

Answer 6

Define and initialize a Scanner variable named inSS that creates an input string stream using the String variable myStrLine.

Ans: Scanner inSS = new Scanner(myStrLine);