# Class ServletOutputStream

java.lang.Object
java.io.OutputStream
jakarta.servlet.ServletOutputStream

All Implemented Interfaces:
  `Closeable`, `Flushable`, `AutoCloseable`

public abstract class ServletOutputStream extends OutputStream
Provides an output stream for sending binary data to the client. A `ServletOutputStream` object is normally retrieved via the `ServletResponse.getOutputStream()` method.

This is an abstract class that the servlet container implements. Subclasses of this class must implement the `java.io.OutputStream.write(int)` method.

See Also:
  - `ServletResponse`

- ## Constructor Summary

  Constructors
  Modifier
  Constructor
  Description
  `protected`
  `ServletOutputStream()`
  Does nothing, because this is an abstract class.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `abstract boolean`
  `isReady()`
  Checks if a non-blocking write will succeed.
  `void`
  `print(boolean b)`
  Writes a `boolean` value to the client, with no carriage return-line feed (CRLF) character at the end.
  `void`
  `print(char c)`
  Writes a character to the client, with no carriage return-line feed (CRLF) at the end.
  `void`
  `print(double d)`
  Writes a `double` value to the client, with no carriage return-line feed (CRLF) at the end.
  `void`
  `print(float f)`
  Writes a `float` value to the client, with no carriage return-line feed (CRLF) at the end.
  `void`
  `print(int i)`
  Writes an int to the client, with no carriage return-line feed (CRLF) at the end.
  `void`
  `print(long l)`
  Writes a `long` value to the client, with no carriage return-line feed (CRLF) at the end.
  `void`
  `print(String s)`
  Writes a `String` to the client, without a carriage return-line feed (CRLF) character at the end.
  `void`
  `println()`
  Writes a carriage return-line feed (CRLF) to the client.
  `void`
  `println(boolean b)`
  Writes a `boolean` value to the client, followed by a carriage return-line feed (CRLF).
  `void`
  `println(char c)`
  Writes a character to the client, followed by a carriage return-line feed (CRLF).
  `void`
  `println(double d)`
  Writes a `double` value to the client, followed by a carriage return-line feed (CRLF).
  `void`
  `println(float f)`
  Writes a `float` value to the client, followed by a carriage return-line feed (CRLF).
  `void`
  `println(int i)`
  Writes an int to the client, followed by a carriage return-line feed (CRLF) character.
  `void`
  `println(long l)`
  Writes a `long` value to the client, followed by a carriage return-line feed (CRLF).
  `void`
  `println(String s)`
  Writes a `String` to the client, followed by a carriage return-line feed (CRLF).
  `abstract void`
  `setWriteListener(WriteListener listener)`
  Sets the `WriteListener` for this `ServletOutputStream` and thereby switches to non-blocking IO.

  ### Methods inherited from class java.io.OutputStream

  `close, flush, nullOutputStream, write, write, write`

  ### Methods inherited from class java.lang.Object

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

- ## Constructor Details

  - ### ServletOutputStream

    protected ServletOutputStream()
    Does nothing, because this is an abstract class.

- ## Method Details

  - ### print

    public void print(String s) throws IOException
    Writes a `String` to the client, without a carriage return-line feed (CRLF) character at the end.
    Parameters:
      `s` - the `String` to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### print

    public void print(boolean b) throws IOException
    Writes a `boolean` value to the client, with no carriage return-line feed (CRLF) character at the end.
    Parameters:
      `b` - the `boolean` value to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### print

    public void print(char c) throws IOException
    Writes a character to the client, with no carriage return-line feed (CRLF) at the end.
    Parameters:
      `c` - the character to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### print

    public void print(int i) throws IOException
    Writes an int to the client, with no carriage return-line feed (CRLF) at the end.
    Parameters:
      `i` - the int to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### print

    public void print(long l) throws IOException
    Writes a `long` value to the client, with no carriage return-line feed (CRLF) at the end.
    Parameters:
      `l` - the `long` value to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### print

    public void print(float f) throws IOException
    Writes a `float` value to the client, with no carriage return-line feed (CRLF) at the end.
    Parameters:
      `f` - the `float` value to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### print

    public void print(double d) throws IOException
    Writes a `double` value to the client, with no carriage return-line feed (CRLF) at the end.
    Parameters:
      `d` - the `double` value to send to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println() throws IOException
    Writes a carriage return-line feed (CRLF) to the client.
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(String s) throws IOException
    Writes a `String` to the client, followed by a carriage return-line feed (CRLF).
    Parameters:
      `s` - the `String` to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(boolean b) throws IOException
    Writes a `boolean` value to the client, followed by a carriage return-line feed (CRLF).
    Parameters:
      `b` - the `boolean` value to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(char c) throws IOException
    Writes a character to the client, followed by a carriage return-line feed (CRLF).
    Parameters:
      `c` - the character to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(int i) throws IOException
    Writes an int to the client, followed by a carriage return-line feed (CRLF) character.
    Parameters:
      `i` - the int to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(long l) throws IOException
    Writes a `long` value to the client, followed by a carriage return-line feed (CRLF).
    Parameters:
      `l` - the `long` value to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(float f) throws IOException
    Writes a `float` value to the client, followed by a carriage return-line feed (CRLF).
    Parameters:
      `f` - the `float` value to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### println

    public void println(double d) throws IOException
    Writes a `double` value to the client, followed by a carriage return-line feed (CRLF).
    Parameters:
      `d` - the `double` value to write to the client
    Throws:
      `IOException` - if an input or output exception occurred

  - ### isReady

    public abstract boolean isReady()
    Checks if a non-blocking write will succeed. If this returns `false`, it will cause a callback to `WriteListener.onWritePossible()` when the buffer has emptied. If this method returns `false` no further data must be written until the container calls `WriteListener.onWritePossible()`.
    Returns:
      `true` if data can be written, else `false`
    Since:
      Servlet 3.1

  - ### setWriteListener

    public abstract void setWriteListener(WriteListener listener)
    Sets the `WriteListener` for this `ServletOutputStream` and thereby switches to non-blocking IO. It is only valid to switch to non-blocking IO within async processing or HTTP upgrade processing.
    Parameters:
      `listener` - The non-blocking IO write listener
    Throws:
      `IllegalStateException` - If this method is called if neither async nor HTTP upgrade is in progress or if the `WriteListener` has already been set
      `NullPointerException` - If listener is null
    Since:
      Servlet 3.1