There are a number of typos where both two articles follow each other: ‘a the’ and ‘a an’.

javax.swing.JFileChooser#ACCEPT_ALL_FILE_FILTER_USED_CHANGED_PROPERTY
Identifies whether a the AcceptAllFileFilter is used or not.

java.awt.Graphics#fillPolygon(int[], int[], int)
@param xPoints a an array of {@code x} coordinates.
@param nPoints a the total number of points.

I came across one usage and then used the following regular expressions to search:
 • (?<!@param ?)\ban? the\b
 • (?<!@param ?)\ba an\b
 • (?<!@param ?)\ban a\b
 • (?<!@param ?)\bthe an?\b

The most generic search: (?<!@param ?)\b(?:[Tt]he|[Aa]n?) (?:the|an?)\b
However, it produces lots of results. Yet it doesn't handle the situation where ‘the/an’ are separated with a line break.