java regex replace capture group

certainly! regular expressions (regex) in java are a powerful tool for pattern matching and string manipulation. one common use case is to replace captured groups in a string. this allows you to match specific parts of a string and replace them with new values.

### overview of java regex and capture groups

- `pattern`: a compiled representation of a regex.
- `matcher`: an engine that performs matching operations on a character sequence using a `pattern`.

a capture group is defined by parentheses `()`. when a regex matches a string, the parts of the string that correspond to the capture groups can be referenced in replacements.

### syntax for replacement

in the replacement string, you can refer to capture groups using `$n`, where `n` is the group number (starting from 1).

### example: replacing capture groups

let’s say we have a string with dates in the format `mm-dd-yyyy`, and we want to convert it to the format `yyyy/mm/dd`.

#### step-by-step code example

1. **import the necessary classes**.
2. **define the regex pattern with capture groups**.
3. **create a string to be modified**.
4. **use the `matcher` to find and replace the pattern**.

here’s how you can do it:

### explanation

1. **regex pattern**: the pattern `"(\\d{2})-(\\d{2})-(\\d{4})"` captures:
- `\\d{2}`: two digits for the month (mm)
- `\\d{2}`: two digits for the day (dd)
- `\\d{4}`: four digits for the year (yyyy)

2. **capture groups**:
- group 1 (`$1`): month
- group 2 (`$2`): day
- group 3 (`$3`): year

3. **replacement string**: the replacement pattern `"$3/$1/$2"` rearranges the groups to `yyyy/mm/dd`.

4. **output**: the program outputs the original string and the modified string with the dates in the new format.

### output

when you run the program, you'll see:

### conclusion

this tutorial demonstrates how to use java's regex capabilities to replace par ...

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