Class ThreadLocalPrintStream

java.lang.Object

java.io.OutputStream

java.io.FilterOutputStream

java.io.PrintStream

org.ek9lang.compiler.backend.jvm.ThreadLocalPrintStream

All Implemented Interfaces:

Closeable, Flushable, Appendable, AutoCloseable

public final class ThreadLocalPrintStream
extends PrintStream

A PrintStream that delegates to thread-local outputs. This enables parallel execution where each thread captures its own output without interference from other threads.

When a thread has registered an output stream (via setThreadOutput(ByteArrayOutputStream)), all writes from that thread go to its specific stream. Otherwise, writes go to the fallback stream (typically the original System.out or System.err).

This class is thread-safe. Each thread's output is completely isolated.

Instance-based design allows multiple instances (e.g., one for stdout, one for stderr) each with independent thread-local state.

Used by REPL, bytecode tests, and the EK9 test runner for output capture.

Field Summary

Fields inherited from class FilterOutputStream

out

Constructor Summary

Constructors

Constructor	Description
ThreadLocalPrintStream(PrintStream fallback)	Create a thread-local delegating PrintStream.

Method Summary

Modifier and Type	Method	Description
String	clearAndGet()	Clear the thread-local output and return the captured content.
void	flush()
PrintStream	getFallback()	Get the fallback stream (original System.out or System.err).
void	setThreadOutput(ByteArrayOutputStream output)	Set the output capture for the current thread.
void	write(byte[] b, int off, int len)
void	write(int b)

Methods inherited from class PrintStream

append, append, append, charset, checkError, clearError, close, format, format, print, print, print, print, print, print, print, print, print, printf, printf, println, println, println, println, println, println, println, println, println, println, setError, write, writeBytes

Methods inherited from class OutputStream

nullOutputStream

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ThreadLocalPrintStream

public ThreadLocalPrintStream(PrintStream fallback)

Create a thread-local delegating PrintStream.

Parameters:

fallback - The stream to use when no thread-local output is registered

Method Details

setThreadOutput

public void setThreadOutput(ByteArrayOutputStream output)

Set the output capture for the current thread. All subsequent writes from this thread will go to this stream.

Parameters:

output - The stream to capture output to

clearAndGet

public String clearAndGet()

Clear the thread-local output and return the captured content.

Returns:

The captured output, or empty string if nothing was captured

getFallback

public PrintStream getFallback()

Get the fallback stream (original System.out or System.err).

write

public void write(int b)

Overrides:

write in class PrintStream

write

public void write(@Nonnull
 byte[] b,
 int off,
 int len)

Overrides:

write in class PrintStream

flush

public void flush()

Specified by:

flush in interface Flushable

Overrides:

flush in class PrintStream