CodeWriter

April 5: The CodeWriter class has been updated with a new version that generates the optimum format.

The CodeWriter class provides essential support for pretty-printing: automatically formatting structured text. When a CodeWriter object is created, two parameters have to be specified: an OutputStream object o and an integer width. The CodeWriter will format text onto o while keeping the width of the output within width characters if possible.

• Download CodeWriter.java
• CodeWriter API Document
• Sample program

It can be a little tricky to get the expected output when you first use CodeWriter. But after some experiments, you will find it is a nice tool. Here are some tips that might shorten your learning time.

• CodeWriter.begin and blocks
  Text is input to the pretty-printer as nested blocks. A block is a formatting unit which starts with a begin method call and ends with the nearest end method call. CodeWriter will try to squeeze the whole block into one line. If this cannot be done, CodeWriter will output the block in several lines according to the allowBreak and newline method calls you make in the block. Suppose the current cursor position is "pos". The first line of the block will start at "pos". All the following lines will start at "pos+n" in which "n" is a parameter of begin method.
   
• newline and allowBreak
newline forces the insertion of a line break. allowBreak merely allows the formatter to insert a line break. If CodeWriter can output a block in one line, all the allowBreak calls in the block will be ignored. However, if there is any newline method call in a block, every allowBreak in the block will incur a line change no matter what. So newline is not recommended unless you don't really don't want the block to sit in one line. When you observe the output of the sample, you will find Block1 and Block3 are similar except one allowBreak in Block1 is replaced by a newline in Block3. You should be able to figure out how the small change affects the output.