Module java.base
Package java.io

Class PrintWriter

java.lang.Object
java.io.Writer
java.io.PrintWriter
All Implemented Interfaces:
Closeable, Flushable, Appendable, AutoCloseable
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().

This class always replaces malformed and unmappable character sequences with the charset's default replacement string. The CharsetEncoder class should be used when more control over the encoding process is required.

Since:
1.1

  • Field Summary

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

    Fields declared in class java.io.Writer

    lock

  • Constructor Summary

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

  • Method Summary

    Modifier and Type
    Method
    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(String format, Object... args)
    Writes a formatted string to this writer using the specified format string and arguments.
    PrintWriter
    format(Locale l, 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(String format, Object... args)
    A convenience method to write a formatted string to this writer using the specified format string and arguments.
    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.
    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()
    Sets the error state of the stream to true.
    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 declared in class java.io.Writer

    nullWriter

    Methods declared in class java.lang.Object

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

  • Field Details

    • out

      protected Writer out
      The underlying character-output stream of this PrintWriter.
      Since:
      1.2

  • Constructor Details

    • 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 charset, or where out is a PrintStream, the charset used by the print stream.
      Parameters:
      out - An output stream
      See Also:

    • 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 charset, or where out is a PrintStream, the charset used by the print stream.
      Parameters:
      out - An output stream
      autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer
      See Also:

    • PrintWriter

      public PrintWriter(OutputStream out, boolean autoFlush, Charset charset)
      Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the specified charset.
      Parameters:
      out - An output stream
      autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer
      charset - A charset
      Since:
      10

    • 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
      See Also:

    • 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(String fileName, Charset charset) throws IOException
      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.
      charset - A charset
      Throws:
      IOException - if an I/O 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:
      10

    • 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
      See Also:

    • 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

    • PrintWriter

      public PrintWriter(File file, Charset charset) throws IOException
      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.
      charset - A charset
      Throws:
      IOException - if an I/O 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:
      10

  • Method Details

    • flush

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

    • 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 AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in class Writer
      See Also:

    • checkError

      public boolean checkError()
      Flushes the stream if it's not closed and checks its error state.
      Returns:
      true if and only if this stream has encountered an IOException, or the setError method has been invoked

    • setError

      protected void setError()
      Sets the error state of the stream to true.

      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
      Throws:
      IndexOutOfBoundsException - If the values of the off and len parameters cause the corresponding method of the underlying Writer to throw an IndexOutOfBoundsException

    • 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
      Throws:
      IndexOutOfBoundsException - If the values of the off and len parameters cause the corresponding method of the underlying Writer to throw an IndexOutOfBoundsException

    • 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 default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      b - The boolean to be printed
      See Also:

    • print

      public void print(char c)
      Prints a character. The character is translated into one or more bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      c - The char to be printed
      See Also:

    • print

      public void print(int i)
      Prints an integer. The string produced by String.valueOf(int) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      i - The int to be printed
      See Also:

    • print

      public void print(long l)
      Prints a long integer. The string produced by String.valueOf(long) is translated into bytes according to the default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      l - The long to be printed
      See Also:

    • 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 default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      f - The float to be printed
      See Also:

    • 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 default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      d - The double to be printed
      See Also:

    • print

      public void print(char[] s)
      Prints an array of characters. The characters are converted into bytes according to the default charset, 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
      See Also:

    • 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 default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      s - The String to be printed
      See Also:

    • 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 default charset, and these bytes are written in exactly the manner of the write(int) method.
      Parameters:
      obj - The Object to be printed
      See Also:

    • println

      public void println()
      Terminates the current line by writing the line separator string. The line separator is System.lineSeparator() 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