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Use Logical Operators You can use the && operator to combine classes that define sets of characters. This is particularly useful when you use it combined with the negation operator(^). For example, if you want to specify that any uppercase consonant is acceptable, you could write the expression that matches this as “[A-CG-IM-Z]{2}”. However, this … Read more…

Match Fixed length It is also possible to designate a sequence of fixed length. For example, to specify four-digit numbers, we write [0-9]{4}. The number in the braces { and } denotes the number of repetitions. We can specify the minimum and maximum numbers of repetitions also. Here are the rules: Expression Description X{N} Repeat … Read more…

Match Any Sequence Sometimes you will want to match any sequence that contains one or more characters, in any order, that are part of a set of characters. For example, to match whole words, you want to match any sequence of the letters of the alphabet. One of the easiest ways to do this is … Read more…

Character Classes Regular expression languages also have character classes, which are a way of specifying a list of possible characters that can match any single character in the string you want to match. If you want to specify a character class explicitly, the characters go between square brackets. Therefore, the character class [0123456789] matches any … Read more…

Wildcards with Quantifiers A quantifier following a subsequence of a pattern determines the possibilities for how that subsequence of a pattern can repeat. Although the previous programs show the general technique for using Pattern and Matcher, they don’t show their power. The real benefit of regular expression processing is not seen until wildcards and quantifiers are … Read more…

Quantifier Plus Sign A quantifier following a subsequence of a pattern determines the possibilities for how that subsequence of a pattern can repeat. Let’s take an example. Suppose you want to find specific character in a string. If you take the simplest case, we can say an character is an arbitrary sequence of one or … Read more…