How to Split a String with Letters and Numbers into Alternating Segments in Java?

Separating Letters and Numbers in a String

In Java, you can encounter the need to split a string that contains both letters and digits into alternating segments. For instance, given the string "123abc345def," you might aim for the following result:

x[0] = "123"
x[1] = "abc"
x[2] = "345"
x[3] = "def"

To achieve this precise separation, you can employ the following regular expression:

str.split("(?<=\D)(?=\d)|(?<=\d)(?=\D)");

This pattern splits the string at specific points based on two conditions:

• (?<=D)(?=\d): Matches positions immediately after a non-digit character (D) and immediately before a digit (d). This condition identifies the start of a numerical segment.
• (?<=d)(?=\D): Matches positions immediately after a digit and immediately before a non-digit character. This condition identifies the start of a letter segment.

By splitting the string at these positions, you can isolate the alternating segments of letters and numbers.

Explanation of the Regexp:

• \D: Matches any non-digit character.
• \d: Matches any digit character.
• (?<=): Positive lookbehind, matching a pattern immediately before the current position.
• (?=): Positive lookahead, matching a pattern immediately after the current position.

Example Usage:

String str = "123abc345def";
String[] x = str.split("(?<=\D)(?=\d)|(?<=\d)(?=\D)");

After executing the above code, the x array will contain the alternating segments as desired:

x[0] = "123"
x[1] = "abc"
x[2] = "345"
x[3] = "def"

This technique enables you to efficiently separate letters and digits in a string, allowing you to process them according to their types.

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