Java; Replace String (using regular expressions)?

Question

As part of the project for school, I need to replace the line from the form:

5 * x^3 - 6 * x^1 + 1 

to something like:

 5x<sup>3</sup> - 6x<sup>1</sup> + 1 

I believe that this can be done with regular expressions, but I still don't know how to do it.

Can you lend me a hand?

PS The actual purpose is to implement an application for processing polynomial Java processing, and I use this to pass polyomial.toString () from the model to the view, and I want it to be displayed using the html tags beautifully.

Answer 1

 str.replaceAll("\\^([0-9]+)", "<sup>$1</sup>"); 

Answer 2

 private String removeScript(String content) { Pattern p = Pattern.compile("<script[^>]*>(.*?)</script>", Pattern.DOTALL | Pattern.CASE_INSENSITIVE); return p.matcher(content).replaceAll(""); } 

Answer 3

 String input = "hello I'm a java dev" + "no job experience needed" + "senior software engineer" + "java job available for senior software engineer"; String fixedInput = input.replaceAll("(java|job|senior)", "<b>$1</b>"); 

Answer 4

 import java.util.regex.PatternSyntaxException; // (:?\d+) \* x\^(:?\d+) // // Options: ^ and $ match at line breaks // // Match the regular expression below and capture its match into backreference number 1 «(:?\d+)» // Match the character ":" literally «:?» // Between zero and one times, as many times as possible, giving back as needed (greedy) «?» // Match a single digit 0..9 «\d+» // Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+» // Match the character " " literally « » // Match the character "*" literally «\*» // Match the characters " x" literally « x» // Match the character "^" literally «\^» // Match the regular expression below and capture its match into backreference number 2 «(:?\d+)» // Match the character ":" literally «:?» // Between zero and one times, as many times as possible, giving back as needed (greedy) «?» // Match a single digit 0..9 «\d+» // Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+» try { String resultString = subjectString.replaceAll("(?m)(:?\\d+) \\* x\\^(:?\\d+)", "$1x<sup>$2</sup>"); } catch (PatternSyntaxException ex) { // Syntax error in the regular expression } catch (IllegalArgumentException ex) { // Syntax error in the replacement text (unescaped $ signs?) } catch (IndexOutOfBoundsException ex) { // Non-existent backreference used the replacement text } 

Answer 5

If this is for any general mathematical expression, and parentheses are acceptable, it will be very difficult (perhaps impossible) to do this with regular expressions.

If the only replacements are the ones you showed, it’s not so difficult to do. Align * first, then use the grab as shown in the figure so that Can Berk Güder processes ^ .

Answer 6

What is your polynomial? If you "process" it, I will introduce some kind of tree of subexpressions generated at some point, and would think that it would be much easier to use this to generate your string than to re-analyze the raw expression with the regular expression.

Just throw another way of thinking. I'm not sure what else is going on in your application.

Answer 7

 "5 * x^3 - 6 * x^1 + 1".replaceAll("\\W*\\*\\W*","").replaceAll("\\^(\\d+)","<sup>$1</sup>"); 

note that combining both substitutions in a single regex / substitution would be a bad choice, because more general expressions like x^3 - 6 * x .

Answer 8

 class Replacement { public static void main(String args[]) { String Main = "5 * x^3 - 6 * x^1 + 1"; String replaced = Main.replaceAll("(?m)(:?\\d+) \\* x\\^(:?\\d+)", "$1x<sup>$2</sup>"); System.out.println(replaced); } } 

Answer 9

You will want to look at the capture in regular expression to handle the wrapper 3 in ^ 3.

Answer 10

Try the following:

 String str = "5 * x^3 - 6 * x^1 + 1"; String replacedStr = str.replaceAll("\\^(\\d+)", "<sup>\$1</sup>"); 

Be sure to import java.util.regex.

Answer 11

Take a look at antlr4. This will allow you to make significant progress in creating a tree structure than just regular expressions.

https://github.com/antlr/grammars-v4/tree/master/calculator (calculator.g4 contains the desired grammar)

In a nutshell, you define a grammar for parsing an expression, using antlr to generate java code, and adding callbacks to handle evaluations when building a tree.

Answer 12

Try this, maybe not the best way. but it works

 String str = "5 * x^3 - 6 * x^1 + 1"; str = str.replaceAll("(?x)(\\d+)(\\s+?\\*?\\s+?)(\\w+?)(\\^+?)(\\d+?)", "$1$3<sup>$5</sup>"); System.out.println(str);