Documentation of 'org.clapper.util.io.WordWrapWriter' Java class
WordWrapWriter
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org.clapper.util.io

Class WordWrapWriter

  • All Implemented Interfaces:
    java.io.Closeable, java.io.Flushable, java.lang.Appendable, java.lang.AutoCloseable

    public class WordWrapWriter
extends java.io.PrintWriter

    The WordWrapWriter class is a filter class. A WordWrapWriter object wraps a Writer or OutputStream object, filtering output to the wrapped object so that output lines are broken on word boundaries and fit nicely within the proscribed output width. Messages may be written with prefixes or without them, depending upon various settings in the WordWrapWriter object; the columnar width of the output object can be controlled, as well.

    For example, the long message

    Unable to open file /usr/local/etc/wombat: No such file or directory

    might appear like this without a prefix:

     Unable to open file /usr/local/etc/wombat: No such file or
 directory

    and like this if the prefix is "myprog:"

     myprog: Unable to open file /usr/local/etc/wombat: No such
         file or directory

    Alternatively, if the output width is shortened, the same message can be made to wrap something like this:

     myprog: Unable to open file
         /usr/local/etc/wombat:
         No such file or
         directory

    Note how the WordWrapWriter output's logic will "tab" past the prefix on wrapped lines.

    WordWrapWriter objects also support the notion of an indentation level, which is independent of the prefix. A non-zero indentation level causes each line, including the first line, to be indented that many characters. Thus, calling setIndentation() with a value of 4 will cause each output line to be preceded by 4 blanks. (It's also possible to change the indentation character from a blank to any other character. See setIndentationChar() for details.)

    The logic is predicated on the notion of a "message"; that is, a WordWrapWriter object has to know where a message begins and ends, so it can tell when to write the prefix, reset its internal column count, etc. The class's notion of a message is straightforward: A message consists of all characters written to the object via one of the write() methods, up to and including either an embedded newline or a call to the flush() method. The println() methods implicitly call flush(), as does any write() method that encounters an embedded newline. Thus, it's rarely necessary to call flush() manually.

    Notes

    1. The class does not do any special processing of tab characters. Embedded tab characters can have surprising (and unwanted) effects on the rendered output.
    2. Wrapping another WordWrapWriter object is an invitation to trouble.
    3. Technically, this class probably ought to extend the java.io.FilterWriter class, since performs filtering of output written to another underlying Writer or OutputStream. However, I wanted WordWrapWriter to be polymorphically compatible with java.io.PrintWriter, so it could be passed to methods expecting a PrintWriter object; there are more methods that expect a PrintWriter than there are methods that expect a FilterWriter.
    See Also:
    Writer, PrintWriter

    • Field Summary

      Fields 
      Modifier and Type Field and Description
      static int DEFAULT_LINE_LENGTH
      The default line length.

    • Constructor Summary

      Constructors 
      Constructor and Description
      WordWrapWriter(java.io.OutputStream output)
      Build an WordWrapWriter object that will write its output to the specified OutputStream object, using the default line length of 80.
      WordWrapWriter(java.io.OutputStream output, int lineLength)
      Build an WordWrapWriter object that will write its output to the specified OutputStream object, using the specified line length.
      WordWrapWriter(java.io.OutputStream output, int lineLength, int indentSpaces)
      Build an WordWrapWriter object that will write its output to the specified OutputStream object, using the specified line length.
      WordWrapWriter(java.io.PrintWriter output)
      Build an WordWrapWriter object that will write its output to the specified PrintWriter object, using the default line length of 80.
      WordWrapWriter(java.io.PrintWriter output, int lineLength)
      Build an WordWrapWriter object that will write its output to the specified PrintWriter object, using the specified line length.
      WordWrapWriter(java.io.PrintWriter output, int lineLength, int indentSpaces)
      Build an WordWrapWriter object that will write its output to the specified PrintWriter object, using the specified line length.
      WordWrapWriter(java.io.Writer output)
      Build an WordWrapWriter object that will write its output to the specified Writer object, using the default line length of 80.
      WordWrapWriter(java.io.Writer output, int lineLength)
      Build an WordWrapWriter object that will write its output to the specified Writer object, using the specified line length.
      WordWrapWriter(java.io.Writer output, int lineLength, int indentSpaces)
      Build an WordWrapWriter object that will write its output to the specified Writer object, using the specified line length.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method and Description
      boolean checkError()
      Flush the stream and check its error state.
      void close()
      Close the stream, flushing it first.
      void flush()
      Flush the stream.
      int getIndentation()
      Retrieve the current indentation setting for wrapped lines.
      char getIndentationChar()
      Get the current indentation character.
      int getLineLength()
      Retrieve the current line length.
      java.lang.String getPrefix()
      Get the current prefix.
      void print(boolean b)
      Print a boolean.
      void print(char c)
      Print a character.
      void print(char[] s)
      Print an array of characters.
      void print(double d)
      Print a double.
      void print(float f)
      Print a float.
      void print(int i)
      Print an integer.
      void print(long l)
      Print a long.
      void print(java.lang.Object x)
      Print an Object.
      void print(short s)
      Print a short.
      void print(java.lang.String s)
      Print a String.
      void println()
      End the current line.
      void println(boolean b)
      Print a boolean and finish the line.
      void println(char c)
      Print a character and finish the line.
      void println(char[] s)
      Print an array of characters.
      void println(double d)
      Print a double and finish the line.
      void println(float f)
      Print a float and finish the line.
      void println(int i)
      Print an integer.
      void println(long l)
      Print a long and finish the line.
      void println(java.lang.Object x)
      Print an Object and finish the line.
      void println(short s)
      Print a short and finish the line.
      void println(java.lang.String s)
      Print a String and finish the line.
      void setIndentation(int newIndentation)
      Set the indentation value for wrapped lines.
      void setIndentationChar(char c)
      Change the indentation character.
      void setLineLength(int newLineLength)
      Set the line length.
      java.lang.String setPrefix(java.lang.String newPrefix)
      Set the current prefix.
      void write(char[] cbuf)
      Write an array of characters.
      void write(char[] cbuf, int off, int len)
      Write a portion of an array of characters to the underlying output object.
      void write(int c)
      Write a single character.
      void write(java.lang.String s)
      Write a string.
      void write(java.lang.String s, int off, int len)
      Write a portion of a String of characters to the underlying output object.

      • Methods inherited from class java.io.PrintWriter

        append, append, append, format, format, printf, printf

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • DEFAULT_LINE_LENGTH

        public static final int DEFAULT_LINE_LENGTH
        The default line length.
        See Also:
        Constant Field Values

    • Method Detail

      • checkError

        public boolean checkError()
        Flush the stream and check its error state.
        Overrides:
        checkError in class java.io.PrintWriter

      • close

        public void close()
        Close the stream, flushing it first. Closing a previously-closed stream has no effect.
        Specified by:
        close in interface java.io.Closeable
        Specified by:
        close in interface java.lang.AutoCloseable
        Overrides:
        close in class java.io.PrintWriter

      • flush

        public void flush()
        Flush the stream. If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.
        Specified by:
        flush in interface java.io.Flushable
        Overrides:
        flush in class java.io.PrintWriter

      • getIndentation

        public int getIndentation()
        Retrieve the current indentation setting for wrapped lines.
        Returns:
        The indentation setting, a count that indicates how many leading spaces will be emitted on wrapped lines.

      • getIndentationChar

        public char getIndentationChar()
        Get the current indentation character. By default, the indentation character is a blank.
        Returns:
        The current indentation character.
        See Also:
        setIndentationChar(char)

      • getPrefix

        public java.lang.String getPrefix()
        Get the current prefix. The prefix is the string that's displayed before the first line of output; subsequent wrapped lines are tabbed past the prefix.
        Returns:
        the current prefix, or null if there isn't one.
        See Also:
        setPrefix(java.lang.String)

      • getLineLength

        public int getLineLength()
        Retrieve the current line length.
        Returns:
        The line length.

      • setIndentation

        public void setIndentation(int newIndentation)
        Set the indentation value for wrapped lines.
        Parameters:
        newIndentation - The indentation setting, a count that indicates how many leading spaces will be emitted on wrapped lines. A value of 0 disables the feature.
        Throws:
        java.lang.IndexOutOfBoundsException - the value is negative

      • setIndentationChar

        public void setIndentationChar(char c)
        Change the indentation character. By default, the indentation character is a blank.
        Parameters:
        c - The new indentation character.
        See Also:
        getIndentationChar()

      • setLineLength

        public void setLineLength(int newLineLength)
                   throws java.lang.IndexOutOfBoundsException
        Set the line length.
        Parameters:
        newLineLength - The new line length to use. A value of 0 disables wrapping.
        Throws:
        java.lang.IndexOutOfBoundsException - the value is negative

      • setPrefix

        public java.lang.String setPrefix(java.lang.String newPrefix)
        Set the current prefix. The prefix is a string that's displayed before the first line of output; subsequent wrapped lines are tabbed past the prefix. For instance, suppose the prefix is set to "foo: ". A message emitted while "foo: " is the prefix might look like this: 
         foo: Unable to access the frammistat: No
      such file or device.
        Parameters:
        newPrefix - The new prefix to be set
        Returns:
        the old prefix, or null if there isn't one.
        See Also:
        getPrefix()

      • print

        public void print(boolean b)
        Print a boolean.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        b - The boolean to print

      • print

        public void print(char c)
        Print a character.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        c - The character to print

      • print

        public void print(char[] s)
        Print an array of characters.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        s - The array of characters to print

      • print

        public void print(double d)
        Print a double.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        d - The double floating point number to print

      • print

        public void print(float f)
        Print a float.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        f - The floating point number to print

      • print

        public void print(int i)
        Print an integer.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        i - The integer to print

      • print

        public void print(long l)
        Print a long.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        l - The long to print

      • print

        public void print(short s)
        Print a short.
        Parameters:
        s - The short to print

      • print

        public void print(java.lang.String s)
        Print a String.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        s - The String to print.

      • print

        public void print(java.lang.Object x)
        Print an Object.
        Overrides:
        print in class java.io.PrintWriter
        Parameters:
        x - The object to print.

      • println

        public void println()
        End the current line.
        Overrides:
        println in class java.io.PrintWriter

      • println

        public void println(boolean b)
        Print a boolean and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        b - The boolean to print

      • println

        public void println(char c)
        Print a character and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        c - The character to print

      • println

        public void println(char[] s)
        Print an array of characters.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        s - The array of characters to print

      • println

        public void println(double d)
        Print a double and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        d - The double floating point number to print

      • println

        public void println(float f)
        Print a float and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        f - The floating point number to print

      • println

        public void println(int i)
        Print an integer.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        i - The integer to print

      • println

        public void println(long l)
        Print a long and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        l - The long to print

      • println

        public void println(short s)
        Print a short and finish the line.
        Parameters:
        s - The short to print

      • println

        public void println(java.lang.String s)
        Print a String and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        s - The String to print.

      • println

        public void println(java.lang.Object x)
        Print an Object and finish the line.
        Overrides:
        println in class java.io.PrintWriter
        Parameters:
        x - The object to print.

      • write

        public void write(int c)
        Write a single character. This method is called by all other write(), print() and println() methods. Thus, subclasses that wish to preprocess (or intercept) the output only have to override this method.
        Overrides:
        write in class java.io.PrintWriter
        Parameters:
        c - Character to write

      • write

        public void write(char[] cbuf,
                  int off,
                  int len)
        Write a portion of an array of characters to the underlying output object. Assumes the characters represent the start of a new line. Each line is indented according to this object's defined indentation level.
        Overrides:
        write in class java.io.PrintWriter
        Parameters:
        cbuf - Array of characters
        off - Offset from which to start writing characters
        len - Number of characters to write

      • write

        public void write(java.lang.String s,
                  int off,
                  int len)
        Write a portion of a String of characters to the underlying output object. Assumes the characters represent the start of a new line. Each line is indented according to this object's defined indentation level.
        Overrides:
        write in class java.io.PrintWriter
        Parameters:
        s - String from which to write
        off - Offset from which to start writing characters
        len - Number of characters to write

      • write

        public void write(java.lang.String s)
        Write a string.
        Overrides:
        write in class java.io.PrintWriter
        Parameters:
        s - String to write

      • write

        public void write(char[] cbuf)
        Write an array of characters.
        Overrides:
        write in class java.io.PrintWriter
        Parameters:
        cbuf - Array of characters to write
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