How do you distinguish between a Java regular expression meta dot and an ordinary dot?

Java Metacharacters vs. Ordinary Characters: Dot and Other Symbols

In Java Regular Expressions (RegEx), the dot (.) is a powerful metacharacter that typically matches any character (except newline). However, it can also be used as an ordinary character, denoting a literal dot.

Distinguishing Meta Dot from Ordinary Dot

To differentiate between the meta dot and the ordinary dot, it is crucial to use backslash () as an escape character.

For meta dot (.): If you wish to treat the dot as a metacharacter, leave it unescaped.

For ordinary dot (.): If you want to match a literal dot, you must escape it as ..

Handling Other Metacharacters

Similar principles apply to other metacharacters with special meanings in RegEx. To use them as ordinary characters, escape them with two backslashes ().

Examples:

• To match the asterisk character () literally, use .
• To match the plus sign ( ) literally, use .
• To match any digit (d), use \d.

Consequences of Escaping Metacharacters

Escaping metacharacters affects their original behaviour. For instance, when the asterisk () is used as a metacharacter, it matches 0 or more occurrences. However, when escaped (), it matches the literal * character and loses its special meaning.

By following these rules, you can effectively handle metacharacters in Java RegEx to match specific character patterns accurately.

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