Module java.base
Package java.io

Class PrintWriter

  • All Implemented Interfaces:
    Closeable,Flushable,Appendable,AutoCloseable
    public classPrintWriterextendsWriter
    Prints formatted representations of objects to a text-output stream. This class implements all of theprint methods found inPrintStream. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.

    Unlike thePrintStream class, if automatic flushing is enabled it will be done only when one of theprintln,printf, orformat 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 invokingcheckError().

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

    Since:
    1.1

    • Field Summary

      Fields 
      Modifier and TypeFieldDescription
      protectedWriterout
      The underlying character-output stream of thisPrintWriter.

    • Constructor Summary

      Constructors 
      ConstructorDescription
      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

      All Methods Instance Methods Concrete Methods 
      Modifier and TypeMethodDescription
      PrintWriterappend​(char c)
      Appends the specified character to this writer.
      PrintWriterappend​(CharSequence csq)
      Appends the specified character sequence to this writer.
      PrintWriterappend​(CharSequence csq, int start, int end)
      Appends a subsequence of the specified character sequence to this writer.
      booleancheckError()
      Flushes the stream if it's not closed and checks its error state.
      protected voidclearError()
      Clears the error state of this stream.
      voidclose()
      Closes the stream and releases any system resources associated with it.
      voidflush()
      Flushes the stream.
      PrintWriterformat​(String format,Object... args)
      Writes a formatted string to this writer using the specified format string and arguments.
      PrintWriterformat​(Locale l,String format,Object... args)
      Writes a formatted string to this writer using the specified format string and arguments.
      voidprint​(boolean b)
      Prints a boolean value.
      voidprint​(char c)
      Prints a character.
      voidprint​(char[] s)
      Prints an array of characters.
      voidprint​(double d)
      Prints a double-precision floating-point number.
      voidprint​(float f)
      Prints a floating-point number.
      voidprint​(int i)
      Prints an integer.
      voidprint​(long l)
      Prints a long integer.
      voidprint​(Object obj)
      Prints an object.
      voidprint​(String s)
      Prints a string.
      PrintWriterprintf​(String format,Object... args)
      A convenience method to write a formatted string to this writer using the specified format string and arguments.
      PrintWriterprintf​(Locale l,String format,Object... args)
      A convenience method to write a formatted string to this writer using the specified format string and arguments.
      voidprintln()
      Terminates the current line by writing the line separator string.
      voidprintln​(boolean x)
      Prints a boolean value and then terminates the line.
      voidprintln​(char x)
      Prints a character and then terminates the line.
      voidprintln​(char[] x)
      Prints an array of characters and then terminates the line.
      voidprintln​(double x)
      Prints a double-precision floating-point number and then terminates the line.
      voidprintln​(float x)
      Prints a floating-point number and then terminates the line.
      voidprintln​(int x)
      Prints an integer and then terminates the line.
      voidprintln​(long x)
      Prints a long integer and then terminates the line.
      voidprintln​(Object x)
      Prints an Object and then terminates the line.
      voidprintln​(String x)
      Prints a String and then terminates the line.
      protected voidsetError()
      Indicates that an error has occurred.
      voidwrite​(char[] buf)
      Writes an array of characters.
      voidwrite​(char[] buf, int off, int len)
      Writes A Portion of an array of characters.
      voidwrite​(int c)
      Writes a single character.
      voidwrite​(String s)
      Writes a string.
      voidwrite​(String s, int off, int len)
      Writes a portion of a string.

    • Field Detail

      • out

        protected Writer out
        The underlying character-output stream of thisPrintWriter.
        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, theprintln,printf, orformat 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(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, theprintln,printf, orformat methods will flush the output buffer
        See Also:
        OutputStreamWriter(java.io.OutputStream)

      • 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, theprintln,printf, orformat methods will flush the output buffer
        charset - Acharset
        Since:
        10

      • PrintWriter

        public PrintWriter​(String fileName)            throwsFileNotFoundException
        Creates a new PrintWriter, without automatic line flushing, with the specified file name. This convenience constructor creates the necessary intermediateOutputStreamWriter, which will encode characters using thedefault 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 andcheckWrite(fileName) denies write access to the file
        Since:
        1.5

      • PrintWriter

        public PrintWriter​(String fileName,String csn)            throwsFileNotFoundException,UnsupportedEncodingException
        Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediateOutputStreamWriter, 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 supportedcharset
        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 andcheckWrite(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)            throwsIOException
        Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediateOutputStreamWriter, 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 - Acharset
        Throws:
        IOException - if an I/O error occurs while opening or creating the file
        SecurityException - If a security manager is present andcheckWrite(fileName) denies write access to the file
        Since:
        10

      • PrintWriter

        public PrintWriter​(File file)            throwsFileNotFoundException
        Creates a new PrintWriter, without automatic line flushing, with the specified file. This convenience constructor creates the necessary intermediateOutputStreamWriter, which will encode characters using thedefault 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 andcheckWrite(file.getPath()) denies write access to the file
        Since:
        1.5

      • PrintWriter

        public PrintWriter​(File file,String csn)            throwsFileNotFoundException,UnsupportedEncodingException
        Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediateOutputStreamWriter, 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 supportedcharset
        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 andcheckWrite(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)            throwsIOException
        Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediateOutputStreamWriter, 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 - Acharset
        Throws:
        IOException - if an I/O error occurs while opening or creating the file
        SecurityException - If a security manager is present andcheckWrite(file.getPath()) denies write access to the file
        Since:
        10

    • Method Detail

      • 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()

      • 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 ofcheckError() to returntrue untilclearError() is invoked.

      • clearError

        protected void clearError()
        Clears the error state of this stream.

        This method will cause subsequent invocations ofcheckError() to returnfalse until another write operation fails and invokessetError().

        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 theoff andlen parameters cause the corresponding method of the underlyingWriter to throw anIndexOutOfBoundsException

      • 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 theoff andlen parameters cause the corresponding method of the underlyingWriter to throw anIndexOutOfBoundsException

      • 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 byString.valueOf(boolean) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of thewrite(int) method.
        Parameters:
        b - Theboolean 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 thewrite(int) method.
        Parameters:
        c - Thechar to be printed

      • print

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

      • print

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

      • print

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

      • print

        public void print​(double d)
        Prints a double-precision floating-point number. The string produced byString.valueOf(double) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of thewrite(int) method.
        Parameters:
        d - Thedouble 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 thewrite(int) method.
        Parameters:
        s - The array of chars to be printed
        Throws:
        NullPointerException - Ifs isnull

      • print

        public void print​(String s)
        Prints a string. If the argument isnull 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 thewrite(int) method.
        Parameters:
        s - TheString to be printed

      • print

        public void print​(Object obj)
        Prints an object. The string produced by theString.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 thewrite(int) method.
        Parameters:
        obj - TheObject 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 propertyline.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 invokesprint(boolean) and thenprintln().
        Parameters:
        x - theboolean value to be printed

      • println

        public void println​(char x)
        Prints a character and then terminates the line. This method behaves as though it invokesprint(char) and thenprintln().
        Parameters:
        x - thechar value to be printed

      • println

        public void println​(int x)
        Prints an integer and then terminates the line. This method behaves as though it invokesprint(int) and thenprintln().
        Parameters:
        x - theint 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 invokesprint(long) and thenprintln().
        Parameters:
        x - thelong 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 invokesprint(float) and thenprintln().
        Parameters:
        x - thefloat 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 invokesprint(double) and thenprintln().
        Parameters:
        x - thedouble 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 invokesprint(char[]) and thenprintln().
        Parameters:
        x - the array ofchar values to be printed

      • println

        public void println​(String x)
        Prints a String and then terminates the line. This method behaves as though it invokesprint(String) and thenprintln().
        Parameters:
        x - theString 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 invokesprint(String) and thenprintln().
        Parameters:
        x - TheObject 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 formout.printf(format, args) behaves in exactly the same way as the invocation

             out.format(format, args)

        Parameters:
        format - A format string as described inFormat 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 byThe Java™ Virtual Machine Specification. The behaviour on anull argument depends on theconversion.
        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 theDetails section of the formatter class specification.
        NullPointerException - If theformat isnull
        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 formout.printf(l, format, args) behaves in exactly the same way as the invocation

             out.format(l, format, args)

        Parameters:
        l - Thelocale to apply during formatting. Ifl isnull then no localization is applied.
        format - A format string as described inFormat 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 byThe Java™ Virtual Machine Specification. The behaviour on anull argument depends on theconversion.
        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 theDetails section of the formatter class specification.
        NullPointerException - If theformat isnull
        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 byLocale.getDefault(), regardless of any previous invocations of other formatting methods on this object.

        Parameters:
        format - A format string as described inFormat 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 byThe Java™ Virtual Machine Specification. The behaviour on anull argument depends on theconversion.
        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 theDetails section of the Formatter class specification.
        NullPointerException - If theformat isnull
        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 - Thelocale to apply during formatting. Ifl isnull then no localization is applied.
        format - A format string as described inFormat 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 byThe Java™ Virtual Machine Specification. The behaviour on anull argument depends on theconversion.
        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 theDetails section of the formatter class specification.
        NullPointerException - If theformat isnull
        Since:
        1.5

      • append

        public PrintWriter append​(CharSequence csq)
        Appends the specified character sequence to this writer.

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

             out.write(csq.toString())

        Depending on the specification oftoString for the character sequencecsq, the entire sequence may not be appended. For instance, invoking thetoString 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. Ifcsq isnull, 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 formout.append(csq, start, end) whencsq is notnull, 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. Ifcsq isnull, then characters will be appended as ifcsq 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 - Ifstart orend are negative,start is greater thanend, orend is greater thancsq.length()
        Since:
        1.5

      • append

        public PrintWriter append​(char c)
        Appends the specified character to this writer.

        An invocation of this method of the formout.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