Module com.google.googlejavaformat
Package com.google.googlejavaformat.java

Class Formatter

java.lang.Object
com.google.googlejavaformat.java.Formatter
@Immutable public final class Formatter extends Object
This is google-java-format, a new Java formatter that follows the Google Java Style Guide quite precisely---to the letter and to the spirit.

This formatter uses the javac parser to generate an AST. Because the AST loses information about the non-tokens in the input (including newlines, comments, etc.), and even some tokens (e.g., optional commas or semicolons), this formatter lexes the input again and follows along in the resulting list of tokens. Its lexer splits all multi-character operators (like ">>") into multiple single-character operators. Each non-token is assigned to a token---non-tokens following a token on the same line go with that token; those following go with the next token--- and there is a final EOF token to hold final comments.

The formatter walks the AST to generate a Greg Nelson/Derek Oppen-style list of formatting Ops [1--2] that then generates a structured Doc. Each AST node type has a visitor to emit a sequence of Ops for the node.

Some data-structure operations are easier in the list of Ops, while others become easier in the Doc. The Ops are walked to attach the comments. As the Ops are generated, missing input tokens are inserted and incorrect output tokens are dropped, ensuring that the output matches the input even in the face of formatter errors. Finally, the formatter walks the Doc to format it in the given width.

This formatter also produces data structures of which tokens and comments appear where on the input, and on the output, to help output a partial reformatting of a slightly edited input.

Instances of the formatter are immutable and thread-safe.

[1] Nelson, Greg, and John DeTreville. Personal communication.

[2] Oppen, Derek C. "Prettyprinting". ACM Transactions on Programming Languages and Systems, Volume 2 Issue 4, Oct. 1980, pp. 465–483.

  • Field Details

  • Constructor Details

    • Formatter

      public Formatter()
      A new Formatter instance with default options.

    • Formatter

      public Formatter(JavaFormatterOptions options)

  • Method Details