This article aims to provide a clear and easy-to-understand Java tutorial for parsing strings containing tone adjustment instructions. By using regular expressions, we can extract instrument names, adjustment directions, and adjustment quantities from complex input strings. This tutorial explains the code implementation in detail and provides examples to help readers understand how to deal with such problems in Java.

Parse tone adjustment instructions using regular expressions

In the music field, fine-tuning of tones is crucial. In the program, we may need to parse strings containing the instrument name, adjustment direction (tighten or relax), and adjustment amount. At this time, the regular expression comes in handy.

Introduction to regular expressions

Regular expressions are a powerful text matching tool that can be used to find and replace strings that conform to specific patterns. In Java, the java.util.regex package provides support for regular expressions.

Code implementation

The following code shows how to parse tone adjustment instructions using regular expressions:

 import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class HarpTuning {

    public static void main(String[] args) {
        String[] inputs = { "AFB 8HC-4", "AFB 8SC-4H-2GDPE 9" };
        Pattern pattern = Pattern.compile("(\\D )([ -])(\\d )"); // Match pattern: non-numeric characters plus or negative sign numeric characters for (String s: inputs) {
            System.out.printf("For %s%n", s);
            Matcher matcher = pattern.matcher(s);
            while (matcher.find()) {
                String instrument = matcher.group(1); // Musical instrument name String direction = matcher.group(2).equals(" ") ? "tighten" : "loosen"; // Adjustment direction String amount = matcher.group(3); // Adjustment amount System.out.printf("%s %s %s%n", instrument, direction, amount);
            }
        }
    }
}

Code explanation:

1. Import the necessary classes: Import the java.util.regex.Matcher and java.util.regex.Pattern classes for regular expression operations.
2. Define an input string array: The inputs array contains the tone adjustment instruction string that needs to be parsed.
3. Compile regular expressions: Pattern.compile("(\\D )([ -])(\\d )") Creates a Pattern object that represents the regular expression.
   • (\\D): Match one or more non-numeric characters and capture them into the first group (instrument name).
   • ([ -]): Match a plus or minus sign and capture it into the second group (adjust the orientation).
   • (\\d): Match one or more numeric characters and capture them into the third group (adjust the amount).
4. Loop through input strings: Loop through each string in the inputs array using for loop.
5. Create a Matcher object: pattern.matcher(s) Creates a Matcher object that is used to find subsequences that match regular expressions in the input string.
6. Find matching subsequences: while (matcher.find()) Loops to find all subsequences in the input string that match the regular expression.
7. Extract grouping information:
   • matcher.group(1): Gets the contents of the first group (instrument name).
   • matcher.group(2): Gets the contents of the second group (adjust the orientation) and converts it to a "tighten" or "loosen" string using the ternary operator.
   • matcher.group(3): Get the content of the third group (adjustment amount).
8. Print result: System.out.printf("%s %s %s%n", instrument, direction, amount) Prints the extracted instrument name, adjustment direction, and adjustment amount.

Sample output

Run the above code and you will get the following output:

 For AFB 8HC-4
AFB tighten 8
HC loosen 4
For AFB 8SC-4H-2GDPE 9
AFB tighten 8
SC loosen 4
H loosen 2
GDPE tighten 9

Things to note

• Correctness of regular expressions: Ensure that regular expressions can accurately match the pattern of the target string.
• Grouped index: The index of the group() method starts from 1, and group(0) represents the entire matching string.
• Exception handling: In actual applications, the input string format error should be considered and appropriate exception handling should be carried out.

Summarize

This tutorial describes how to use regular expressions to parse strings containing tone adjustment instructions. By using regular expressions reasonably, we can easily extract the required information from complex text data. This method is not only suitable for parsing tone adjustment instructions, but also for other similar text processing scenarios. I hope this tutorial can help readers better understand and apply regular expressions.

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