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package java.util.logging;

A Formatter provides support for formatting LogRecords.

Typically each logging Handler will have a Formatter associated
with it.  The Formatter takes a LogRecord and converts it to
a string.

Some formatters (such as the XMLFormatter) need to wrap head
and tail strings around a set of formatted records. The getHeader
and getTail methods can be used to obtain these strings.
Since:
1.4/**
 * A Formatter provides support for formatting LogRecords.
 * <p>
 * Typically each logging Handler will have a Formatter associated
 * with it.  The Formatter takes a LogRecord and converts it to
 * a string.
 * <p>
 * Some formatters (such as the XMLFormatter) need to wrap head
 * and tail strings around a set of formatted records. The getHeader
 * and getTail methods can be used to obtain these strings.
 *
 * @since 1.4
 */

public abstract class Formatter {

    
Construct a new formatter.
/**
     * Construct a new formatter.
     */
    protected Formatter() {
    }

    
Format the given log record and return the formatted string.
 The resulting formatted String will normally include a localized and formatted version of the LogRecord's message field. It is recommended to use the formatMessage convenience method to localize and format the message field. 
Params:
record – the log record to be formatted.
Returns:
the formatted log record/**
     * Format the given log record and return the formatted string.
     * <p>
     * The resulting formatted String will normally include a
     * localized and formatted version of the LogRecord's message field.
     * It is recommended to use the {@link Formatter#formatMessage}
     * convenience method to localize and format the message field.
     *
     * @param record the log record to be formatted.
     * @return the formatted log record
     */
    public abstract String format(LogRecord record);


    
Return the header string for a set of formatted records.

This base class returns an empty string, but this may be
overridden by subclasses.
Params:
h –  The target handler (can be null)
Returns:
 header string/**
     * Return the header string for a set of formatted records.
     * <p>
     * This base class returns an empty string, but this may be
     * overridden by subclasses.
     *
     * @param   h  The target handler (can be null)
     * @return  header string
     */
    public String getHead(Handler h) {
        return "";
    }

    
Return the tail string for a set of formatted records.

This base class returns an empty string, but this may be
overridden by subclasses.
Params:
h –  The target handler (can be null)
Returns:
 tail string/**
     * Return the tail string for a set of formatted records.
     * <p>
     * This base class returns an empty string, but this may be
     * overridden by subclasses.
     *
     * @param   h  The target handler (can be null)
     * @return  tail string
     */
    public String getTail(Handler h) {
        return "";
    }


    
Localize and format the message string from a log record.  This
method is provided as a convenience for Formatter subclasses to
use when they are performing formatting.

The message string is first localized to a format string using
the record's ResourceBundle.  (If there is no ResourceBundle,
or if the message key is not found, then the key is used as the
format string.)  The format String uses java.text style
formatting.

If there are no parameters, no formatter is used.
Otherwise, if the string contains "{<digit>" where <digit> is in [0-9], java.text.MessageFormat is used to format the string. 
Otherwise no formatting is performed.

Params:
record –  the log record containing the raw message
Returns:
  a localized and formatted message/**
     * Localize and format the message string from a log record.  This
     * method is provided as a convenience for Formatter subclasses to
     * use when they are performing formatting.
     * <p>
     * The message string is first localized to a format string using
     * the record's ResourceBundle.  (If there is no ResourceBundle,
     * or if the message key is not found, then the key is used as the
     * format string.)  The format String uses java.text style
     * formatting.
     * <ul>
     * <li>If there are no parameters, no formatter is used.
     * <li>Otherwise, if the string contains "{{@literal<digit>}"
     *     where {@literal <digit>} is in [0-9],
     *     java.text.MessageFormat is used to format the string.
     * <li>Otherwise no formatting is performed.
     * </ul>
     *
     * @param  record  the log record containing the raw message
     * @return   a localized and formatted message
     */
    public String formatMessage(LogRecord record) {
        String format = record.getMessage();
        java.util.ResourceBundle catalog = record.getResourceBundle();
        if (catalog != null) {
            try {
                format = catalog.getString(format);
            } catch (java.util.MissingResourceException ex) {
                // Drop through.  Use record message as format
            }
        }
        // Do the formatting.
        try {
            Object parameters[] = record.getParameters();
            if (parameters == null || parameters.length == 0) {
                // No parameters.  Just return format string.
                return format;
            }
            // Is it a java.text style format?
            // Ideally we could match with
            // Pattern.compile("\\{\\d").matcher(format).find())
            // However the cost is 14% higher, so we cheaply use indexOf
            // and charAt to look for that pattern.
            int index = -1;
            int fence = format.length() - 1;
            while ((index = format.indexOf('{', index+1)) > -1) {
                if (index >= fence) break;
                char digit = format.charAt(index+1);
                if (digit >= '0' && digit <= '9') {
                   return java.text.MessageFormat.format(format, parameters);
                }
            }
            return format;

        } catch (Exception ex) {
            // Formatting failed: use localized format string.
            return format;
        }
    }
}