java.io

## Class PrintWriter

- java.lang.Object
- - java.io.Writer
  - - java.io.PrintWriter

- All Implemented Interfaces:
    Closeable, Flushable, Appendable

      public class PrintWriter
      extends Writer

  Prints formatted representations of objects to a text-output stream. This class implements all of the `print` methods found in `PrintStream`. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.

  Unlike the `PrintStream` class, if automatic flushing is enabled it will be done only when one of the `println`, `printf`, or `format` methods is invoked, rather than whenever a newline character happens to be output. These methods use the platform's own notion of line separator rather than the newline character.

  Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking `checkError()`.

  Since:
    JDK1.1

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected Writer` | `out` The underlying character-output stream of this `PrintWriter`.

    - ### Fields inherited from class java.io.Writer

      `lock`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `PrintWriter(File file)` Creates a new PrintWriter, without automatic line flushing, with the specified file.
    `PrintWriter(File file, String csn)` Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
    `PrintWriter(OutputStream out)` Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
    `PrintWriter(OutputStream out, boolean autoFlush)` Creates a new PrintWriter from an existing OutputStream.
    `PrintWriter(String fileName)` Creates a new PrintWriter, without automatic line flushing, with the specified file name.
    `PrintWriter(String fileName, String csn)` Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.
    `PrintWriter(Writer out)` Creates a new PrintWriter, without automatic line flushing.
    `PrintWriter(Writer out, boolean autoFlush)` Creates a new PrintWriter.

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `PrintWriter` | `append(char c)` Appends the specified character to this writer.
    `PrintWriter` | `append(CharSequence csq)` Appends the specified character sequence to this writer.
    `PrintWriter` | `append(CharSequence csq, int start, int end)` Appends a subsequence of the specified character sequence to this writer.
    `boolean` | `checkError()` Flushes the stream if it's not closed and checks its error state.
    `protected void` | `clearError()` Clears the error state of this stream.
    `void` | `close()` Closes the stream and releases any system resources associated with it.
    `void` | `flush()` Flushes the stream.
    `PrintWriter` | `format(Locale l, String format, Object... args)` Writes a formatted string to this writer using the specified format string and arguments.
    `PrintWriter` | `format(String format, Object... args)` Writes a formatted string to this writer using the specified format string and arguments.
    `void` | `print(boolean b)` Prints a boolean value.
    `void` | `print(char c)` Prints a character.
    `void` | `print(char[] s)` Prints an array of characters.
    `void` | `print(double d)` Prints a double-precision floating-point number.
    `void` | `print(float f)` Prints a floating-point number.
    `void` | `print(int i)` Prints an integer.
    `void` | `print(long l)` Prints a long integer.
    `void` | `print(Object obj)` Prints an object.
    `void` | `print(String s)` Prints a string.
    `PrintWriter` | `printf(Locale l, String format, Object... args)` A convenience method to write a formatted string to this writer using the specified format string and arguments.
    `PrintWriter` | `printf(String format, Object... args)` A convenience method to write a formatted string to this writer using the specified format string and arguments.
    `void` | `println()` Terminates the current line by writing the line separator string.
    `void` | `println(boolean x)` Prints a boolean value and then terminates the line.
    `void` | `println(char x)` Prints a character and then terminates the line.
    `void` | `println(char[] x)` Prints an array of characters and then terminates the line.
    `void` | `println(double x)` Prints a double-precision floating-point number and then terminates the line.
    `void` | `println(float x)` Prints a floating-point number and then terminates the line.
    `void` | `println(int x)` Prints an integer and then terminates the line.
    `void` | `println(long x)` Prints a long integer and then terminates the line.
    `void` | `println(Object x)` Prints an Object and then terminates the line.
    `void` | `println(String x)` Prints a String and then terminates the line.
    `protected void` | `setError()` Indicates that an error has occurred.
    `void` | `write(char[] buf)` Writes an array of characters.
    `void` | `write(char[] buf, int off, int len)` Writes A Portion of an array of characters.
    `void` | `write(int c)` Writes a single character.
    `void` | `write(String s)` Writes a string.
    `void` | `write(String s, int off, int len)` Writes a portion of a string.

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

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

- - ### Field Detail

    - #### out

          protected Writer out

      The underlying character-output stream of this `PrintWriter`.
      Since:
        1.2

  - ### Constructor Detail

    - #### PrintWriter

          public PrintWriter(Writer out)

      Creates a new PrintWriter, without automatic line flushing.
      Parameters:
        `out` - A character-output stream

    - #### PrintWriter

          public PrintWriter(Writer out,
                     boolean autoFlush)

      Creates a new PrintWriter.
      Parameters:
        `out` - A character-output stream
        `autoFlush` - A boolean; if true, the `println`, `printf`, or `format` methods will flush the output buffer

    - #### PrintWriter

          public PrintWriter(OutputStream out)

      Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.
      Parameters:
        `out` - An output stream
      See Also:
        `OutputStreamWriter.OutputStreamWriter(java.io.OutputStream)`

    - #### PrintWriter

          public PrintWriter(OutputStream out,
                     boolean autoFlush)

      Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.
      Parameters:
        `out` - An output stream
        `autoFlush` - A boolean; if true, the `println`, `printf`, or `format` methods will flush the output buffer
      See Also:
        `OutputStreamWriter.OutputStreamWriter(java.io.OutputStream)`

    - #### PrintWriter

          public PrintWriter(String fileName)
                      throws FileNotFoundException

      Creates a new PrintWriter, without automatic line flushing, with the specified file name. This convenience constructor creates the necessary intermediate `OutputStreamWriter`, which will encode characters using the default charset for this instance of the Java virtual machine.
      Parameters:
        `fileName` - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
      Throws:
        `FileNotFoundException` - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        `SecurityException` - If a security manager is present and `checkWrite(fileName)` denies write access to the file
      Since:
        1.5

    - #### PrintWriter

          public PrintWriter(String fileName,
                     String csn)
                      throws FileNotFoundException,
                             UnsupportedEncodingException

      Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediate `OutputStreamWriter`, which will encode characters using the provided charset.
      Parameters:
        `fileName` - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        `csn` - The name of a supported charset
      Throws:
        `FileNotFoundException` - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        `SecurityException` - If a security manager is present and `checkWrite(fileName)` denies write access to the file
        `UnsupportedEncodingException` - If the named charset is not supported
      Since:
        1.5

    - #### PrintWriter

          public PrintWriter(File file)
                      throws FileNotFoundException

      Creates a new PrintWriter, without automatic line flushing, with the specified file. This convenience constructor creates the necessary intermediate `OutputStreamWriter`, which will encode characters using the default charset for this instance of the Java virtual machine.
      Parameters:
        `file` - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
      Throws:
        `FileNotFoundException` - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        `SecurityException` - If a security manager is present and `checkWrite(file.getPath())` denies write access to the file
      Since:
        1.5

    - #### PrintWriter

          public PrintWriter(File file,
                     String csn)
                      throws FileNotFoundException,
                             UnsupportedEncodingException

      Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediate `OutputStreamWriter`, which will encode characters using the provided charset.
      Parameters:
        `file` - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        `csn` - The name of a supported charset
      Throws:
        `FileNotFoundException` - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        `SecurityException` - If a security manager is present and `checkWrite(file.getPath())` denies write access to the file
        `UnsupportedEncodingException` - If the named charset is not supported
      Since:
        1.5

  - ### Method Detail

    - #### flush

          public void flush()

      Flushes the stream.
      Specified by:
        `flush` in interface `Flushable`
      Specified by:
        `flush` in class `Writer`
      See Also:
        `checkError()`

    - #### close

          public void close()

      Closes the stream and releases any system resources associated with it. Closing a previously closed stream has no effect.
      Specified by:
        `close` in interface `Closeable`
      Specified by:
        `close` in class `Writer`
      See Also:
        `checkError()`

    - #### checkError

          public boolean checkError()

      Flushes the stream if it's not closed and checks its error state.
      Returns:
        `true` if the print stream has encountered an error, either on the underlying output stream or during a format conversion.

    - #### setError

          protected void setError()

      Indicates that an error has occurred.

      This method will cause subsequent invocations of `checkError()` to return `true` until `clearError()` is invoked.

    - #### clearError

          protected void clearError()

      Clears the error state of this stream.

      This method will cause subsequent invocations of `checkError()` to return `false` until another write operation fails and invokes `setError()`.

      Since:
        1.6

    - #### write

          public void write(int c)

      Writes a single character.
      Overrides:
        `write` in class `Writer`
      Parameters:
        `c` - int specifying a character to be written.

    - #### write

          public void write(char[] buf,
                   int off,
                   int len)

      Writes A Portion of an array of characters.
      Specified by:
        `write` in class `Writer`
      Parameters:
        `buf` - Array of characters
        `off` - Offset from which to start writing characters
        `len` - Number of characters to write

    - #### write

          public void write(char[] buf)

      Writes an array of characters. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.
      Overrides:
        `write` in class `Writer`
      Parameters:
        `buf` - Array of characters to be written

    - #### write

          public void write(String s,
                   int off,
                   int len)

      Writes a portion of a string.
      Overrides:
        `write` in class `Writer`
      Parameters:
        `s` - A String
        `off` - Offset from which to start writing characters
        `len` - Number of characters to write

    - #### write

          public void write(String s)

      Writes a string. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.
      Overrides:
        `write` in class `Writer`
      Parameters:
        `s` - String to be written

    - #### print

          public void print(boolean b)

      Prints a boolean value. The string produced by ``String.valueOf(boolean)`` is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `b` - The `boolean` to be printed

    - #### print

          public void print(char c)

      Prints a character. The character is translated into one or more bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `c` - The `char` to be printed

    - #### print

          public void print(int i)

      Prints an integer. The string produced by ``String.valueOf(int)`` is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `i` - The `int` to be printed
      See Also:
        `Integer.toString(int)`

    - #### print

          public void print(long l)

      Prints a long integer. The string produced by ``String.valueOf(long)`` is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `l` - The `long` to be printed
      See Also:
        `Long.toString(long)`

    - #### print

          public void print(float f)

      Prints a floating-point number. The string produced by ``String.valueOf(float)`` is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `f` - The `float` to be printed
      See Also:
        `Float.toString(float)`

    - #### print

          public void print(double d)

      Prints a double-precision floating-point number. The string produced by ``String.valueOf(double)`` is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `d` - The `double` to be printed
      See Also:
        `Double.toString(double)`

    - #### print

          public void print(char[] s)

      Prints an array of characters. The characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `s` - The array of chars to be printed
      Throws:
        `NullPointerException` - If `s` is `null`

    - #### print

          public void print(String s)

      Prints a string. If the argument is `null` then the string `"null"` is printed. Otherwise, the string's characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `s` - The `String` to be printed

    - #### print

          public void print(Object obj)

      Prints an object. The string produced by the ``String.valueOf(Object)`` method is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the ``write(int)`` method.
      Parameters:
        `obj` - The `Object` to be printed
      See Also:
        `Object.toString()`

    - #### println

          public void println()

      Terminates the current line by writing the line separator string. The line separator string is defined by the system property `line.separator`, and is not necessarily a single newline character (`'\n'`).

    - #### println

          public void println(boolean x)

      Prints a boolean value and then terminates the line. This method behaves as though it invokes ``print(boolean)`` and then ``println()``.
      Parameters:
        `x` - the `boolean` value to be printed

    - #### println

          public void println(char x)

      Prints a character and then terminates the line. This method behaves as though it invokes ``print(char)`` and then ``println()``.
      Parameters:
        `x` - the `char` value to be printed

    - #### println

          public void println(int x)

      Prints an integer and then terminates the line. This method behaves as though it invokes ``print(int)`` and then ``println()``.
      Parameters:
        `x` - the `int` value to be printed

    - #### println

          public void println(long x)

      Prints a long integer and then terminates the line. This method behaves as though it invokes ``print(long)`` and then ``println()``.
      Parameters:
        `x` - the `long` value to be printed

    - #### println

          public void println(float x)

      Prints a floating-point number and then terminates the line. This method behaves as though it invokes ``print(float)`` and then ``println()``.
      Parameters:
        `x` - the `float` value to be printed

    - #### println

          public void println(double x)

      Prints a double-precision floating-point number and then terminates the line. This method behaves as though it invokes ``print(double)`` and then ``println()``.
      Parameters:
        `x` - the `double` value to be printed

    - #### println

          public void println(char[] x)

      Prints an array of characters and then terminates the line. This method behaves as though it invokes ``print(char[])`` and then ``println()``.
      Parameters:
        `x` - the array of `char` values to be printed

    - #### println

          public void println(String x)

      Prints a String and then terminates the line. This method behaves as though it invokes ``print(String)`` and then ``println()``.
      Parameters:
        `x` - the `String` value to be printed

    - #### println

          public void println(Object x)

      Prints an Object and then terminates the line. This method calls at first String.valueOf(x) to get the printed object's string value, then behaves as though it invokes ``print(String)`` and then ``println()``.
      Parameters:
        `x` - The `Object` to be printed.

    - #### printf

          public PrintWriter printf(String format,
                           Object... args)

      A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

      An invocation of this method of the form `out.printf(format, args)` behaves in exactly the same way as the invocation

               out.format(format, args)

      Parameters:
        `format` - A format string as described in Format string syntax.
        `args` - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by the Java Virtual Machine Specification. The behaviour on a `null` argument depends on the conversion.
      Returns:
        This writer
      Throws:
        `IllegalFormatException` - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
        `NullPointerException` - If the `format` is `null`
      Since:
        1.5

    - #### printf

          public PrintWriter printf(Locale l,
                           String format,
                           Object... args)

      A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

      An invocation of this method of the form `out.printf(l, format, args)` behaves in exactly the same way as the invocation

               out.format(l, format, args)

      Parameters:
        `l` - The locale to apply during formatting. If `l` is `null` then no localization is applied.
        `format` - A format string as described in Format string syntax.
        `args` - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by the Java Virtual Machine Specification. The behaviour on a `null` argument depends on the conversion.
      Returns:
        This writer
      Throws:
        `IllegalFormatException` - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
        `NullPointerException` - If the `format` is `null`
      Since:
        1.5

    - #### format

          public PrintWriter format(String format,
                           Object... args)

      Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

      The locale always used is the one returned by `Locale.getDefault()`, regardless of any previous invocations of other formatting methods on this object.

      Parameters:
        `format` - A format string as described in Format string syntax.
        `args` - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by the Java Virtual Machine Specification. The behaviour on a `null` argument depends on the conversion.
      Returns:
        This writer
      Throws:
        `IllegalFormatException` - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the Formatter class specification.
        `NullPointerException` - If the `format` is `null`
      Since:
        1.5

    - #### format

          public PrintWriter format(Locale l,
                           String format,
                           Object... args)

      Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.
      Parameters:
        `l` - The locale to apply during formatting. If `l` is `null` then no localization is applied.
        `format` - A format string as described in Format string syntax.
        `args` - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by the Java Virtual Machine Specification. The behaviour on a `null` argument depends on the conversion.
      Returns:
        This writer
      Throws:
        `IllegalFormatException` - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
        `NullPointerException` - If the `format` is `null`
      Since:
        1.5

    - #### append

          public PrintWriter append(CharSequence csq)

      Appends the specified character sequence to this writer.

      An invocation of this method of the form `out.append(csq)` behaves in exactly the same way as the invocation

               out.write(csq.toString())

      Depending on the specification of `toString` for the character sequence `csq`, the entire sequence may not be appended. For instance, invoking the `toString` method of a character buffer will return a subsequence whose content depends upon the buffer's position and limit.

      Specified by:
        `append` in interface `Appendable`
      Overrides:
        `append` in class `Writer`
      Parameters:
        `csq` - The character sequence to append. If `csq` is `null`, then the four characters `"null"` are appended to this writer.
      Returns:
        This writer
      Since:
        1.5

    - #### append

          public PrintWriter append(CharSequence csq,
                           int start,
                           int end)

      Appends a subsequence of the specified character sequence to this writer.

      An invocation of this method of the form `out.append(csq, start, end)` when `csq` is not `null`, behaves in exactly the same way as the invocation

               out.write(csq.subSequence(start, end).toString())

      Specified by:
        `append` in interface `Appendable`
      Overrides:
        `append` in class `Writer`
      Parameters:
        `csq` - The character sequence from which a subsequence will be appended. If `csq` is `null`, then characters will be appended as if `csq` contained the four characters `"null"`.
        `start` - The index of the first character in the subsequence
        `end` - The index of the character following the last character in the subsequence
      Returns:
        This writer
      Throws:
        `IndexOutOfBoundsException` - If `start` or `end` are negative, `start` is greater than `end`, or `end` is greater than `csq.length()`
      Since:
        1.5

    - #### append

          public PrintWriter append(char c)

      Appends the specified character to this writer.

      An invocation of this method of the form `out.append(c)` behaves in exactly the same way as the invocation

               out.write(c)

      Specified by:
        `append` in interface `Appendable`
      Overrides:
        `append` in class `Writer`
      Parameters:
        `c` - The 16-bit character to append
      Returns:
        This writer
      Since:
        1.5

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