CSV Preferences

Readers and Writers in Super CSV are configured using the CsvPreference class. This class is immutable and is assembled using the Builder pattern.

The preferences available are:

The quote character (used when a cell contains special characters, such as the delimiter char, a quote char, or spans multiple lines).
The delimiter character (separates each cell in a row).
The end of line symbols to use when writing (Windows, Mac and Linux style line breaks are all supported when reading, so this preference won't be used at all for reading).
Whether spaces surrounding a cell need quotes in order to be preserved (see below). The default value is false (quotes aren't required).
Skips comments (what makes up a comment is determined by the CommentMatcher you supply). See the section on skipping comments below for more information.
Use your own encoder when writing CSV. See the section on custom encoders below.
Allows you to enable surrounding quotes for writing (if a column wouldn't normally be quoted because it doesn't contain special characters). See the section on quote modes below.

Predefined preferences

There are four 'ready to use' configurations for typical scenarios.

ConstantQuote charDelimiter charEnd of line symbols

All of these configurations use the default values of:

PreferenceDefault value
skipCommentsfalse (no CommentMatcher used)

Create your own preference

If none of the predefined preferences suit your purposes, you can easily create your own (you're not just limited to CSV files!). For example, the following code snippet creates preferences suitable for reading/writing pipe-delimited files.

private static final CsvPreference PIPE_DELIMITED = new CsvPreference.Builder('"', '|', "\n").build();

Ignoring surrounding spaces if they're not within quotes

In accordance with RFC 4180, the default behaviour of Super CSV is to treat all spaces as important, including spaces surrounding the text in a cell.

This means for reading, a cell with contents    surrounded by spaces    is read with surrounding spaces preserved. And for writing, the same String is written with surrounding spaces and no surrounding quotes (they're not required, as spaces are considered important).

There are some scenarios where this restriction must be relaxed, in particular when the CSV file you're working with assumes that surrounding spaces must be surrounded by quotes, otherwise will be ignored. For this reason, Super CSV allows you to enable the surroundingSpacesNeedQuotes preference.

With surroundingSpacesNeedQuotes enabled, it means that for reading, a cell with contents    surrounded by spaces    would be read as surrounded by spaces (surrounding spaces are trimmed), unless the String has surrounding quotes, e.g. "   surrounded by spaces   ", in which case the spaces are preserved. And for writing, any String containing surrounding spaces will automatically be given surrounding quotes when written in order to preserve the spaces.

You can enable this behaviour by calling surroundingSpacesNeedQuotes(true) on the Builder. You can do this with your own custom preference, or customize an existing preference as shown below.

private static final CsvPreference STANDARD_SURROUNDING_SPACES_NEED_QUOTES = 
    new CsvPreference.Builder(CsvPreference.STANDARD_PREFERENCE).surroundingSpacesNeedQuotes(true).build();

Prior to Super CSV 2.0.0, this behaviour wasn't configurable and surrounding spaces were always trimmed.

Custom quote mode

By default Super CSV only adds surrounding quotes when writing CSV when it contains a delimiter, quote or newline (or if you've enabled surroundingSpacesNeedQuotes and the value has surrounding spaces).

Super CSV provides two alternative quoting modes:

You can also write your own QuoteMode, but please note that this is a means to enable quotes when they're not normally required (you won't be able to disable quotes because then your CSV will not be readable if it contains embedded special characters). Just pass your desired mode to the useQuoteMode() method when building your preferences:

private static final CsvPreference ALWAYS_QUOTE = 
    new CsvPreference.Builder(CsvPreference.STANDARD_PREFERENCE).useQuoteMode(new AlwaysQuoteMode().build();

Custom CSV encoder

Super CSV provides a powerful CsvEncoder, but if you'd like complete control over how your CSV is encoded, then you can supply your own to the useEncoder() method when building your preferences:

private static final CsvPreference CUSTOM_ENCODER = 
    new CsvPreference.Builder(CsvPreference.STANDARD_PREFERENCE).useEncoder(new MyAwesomeEncoder().build();

If you'd like to encode particular columns, but leave other columns unchanged then you can use Super CSV's SelectiveCsvEncoder. This might be useful if you're really concerned with performance and you know that certain columns will never contain special characters. Just be aware that if a column does contain special characters and you don't encode it, you could end up with invalid CSV.

Skipping comments

Although comments aren't part of RFC4180, some CSV files use them so it's useful to be able to skip these lines (or even skip lines because they contain invalid data). You can use one of the predefined comment matchers:

Or if you like you can write your own by implementing the CommentMatcher interface.

Just pass your desired comment matcher to the skipComments() method when building your preferences:

private static final CsvPreference STANDARD_SKIP_COMMENTS = 
    new CsvPreference.Builder(CsvPreference.STANDARD_PREFERENCE).skipComments(new CommentStartsWith("#").build();