MessageFormat

MessageFormat is a class in the Java standard library (java.text) that formats localized messages by combining a pattern with arguments. It enables locale-aware substitution and formatting of numbers, dates, times, and selections (pluralization) within a single string.

Pattern syntax: A pattern consists of literals and argument expressions enclosed in curly braces. An expression has the form {index[,type[,style]]}. index selects the position in the supplied arguments array. type can be number, date, time, or choice; style specifies a locale-specific format (for example date or number formats). If the type is omitted, the argument is formatted using its toString value. Examples: "Hello {0}"; "On {1,date,short} at {2,time,short}." The choice form enables basic pluralization rules.

Usage: Create a MessageFormat with a pattern and a Locale, then call format(Object[]). Patterns can be stored in a ResourceBundle to provide locale-specific strings. Example: MessageFormat fmt = new MessageFormat("Hello {0}, today is {1,date,full}.", Locale.US); String s = fmt.format(new Object[]{"Alice", new Date()});

Escaping: Literal text is quoted with single quotes. To include a literal single quote, use two consecutive quotes. To include a literal { or } in the text, enclose it within quotes.

See also: ResourceBundle, ICU4J MessageFormat, java.text.MessageFormat in the Java API.