Transform Values in Java String with Multiplier

I am interested in multiplying all the numbers in a Java string by a parameter (x) as in the following example where x = 5.

Initial Input: "I have 10 tickets, 5 sodas and 20 snacks to sell."

Target Output: "I have 50 tickets, 25 sodas and 100 snacks to sell."

I tried the following code in Java, but it did not produce the 'Target Output'. I also tried to create a for loop iterating through the string and multiplying any numbers by (x) but this did not work either. How can one produce the desired output in Java?

public String transformOutput(int x){
   string = string.replaceAll("\\d", "\\d" * n)
   return string
}

Get the numbers using regex and use Matcher.appendReplacement to replace

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

public class Test {

    public static void main(String[] args) throws Exception {
        String input = "I have 10 tickets, 5 sodas and 20 snacks to sell.";
        System.out.println(transformOutput(5, input));
    }

    public static String transformOutput(int x, String str) {
        Pattern pattern = Pattern.compile("\\d+");
        Matcher matcher = pattern.matcher(str);
        StringBuffer buffer = new StringBuffer();
        while (matcher.find()) {
            matcher.appendReplacement(buffer, String.valueOf(Integer.parseInt(matcher.group()) * x));
        }
        matcher.appendTail(buffer);        
        return buffer.toString();
    }
}

Using Java 8+ streams:

public String transform(String input, int multiplicator) {
    return Pattern.compile(" ")
            .splitAsStream(input)
            .map(token -> {
                try {
                    return "" + multiplicator * Integer.parseInt(token.trim());
                } catch (NumberFormatException e) {
                    return token;
                }
            })
            .collect(Collectors.joining(" "));
}


@Test
public void test() {
    String input = "I have 10 tickets, 5 sodas and 20 snacks to sell.";
    String output = transform(input, 5);
    assertEquals("I have 50 tickets, 25 sodas and 100 snacks to sell.", output);
}

Here is one way to do it. It works as follows:
Note: Base on your example, I am assuming you don't want numbers embedded in words (e.g foo25).

• Split the string on one or more spaces.

• Stream the subsequent array of tokens.

• selectively map the token to the value if it matches all digits,
  otherwise, just return the word unscathed. This is done by using the
  ternary(?:) operator. The expression a ? b : c says if a is true, do b, else do c.

  .map(st -> st.matches("\\d+") ? (Integer.valueOf(st) * n) + "" : st) <br>

  • if the string, st, matches a number then convert to an integer and multiply by n.
  • otherwise just return the string.

• Then join the stream into a string again using Collectors.join(" ")

  • takes a delimiter and joins concatenates using the supplied delimiter (in this case a space).

import java.util.Arrays;
import java.util.stream.Collectors;

String str =                                                 
		"I have 10 tickets, 5 sodas and 20 snacks to sell."; 
String tstr = transformOutput(str, 5);                       
System.out.println(tstr);                                    
                                                              
                                                                 
public static String transformOutput(String str, int n) {        
	return Arrays                                                
			.stream(str.split("\\s+"))                           
			.map(st -> st.matches("\\d+") ?                      
					(Integer.valueOf(st) * n) + "" : st)         
			.collect(Collectors.joining(" "));                   
	                                                             
}

Prints

I have 50 tickets, 25 sodas and 100 snacks to sell.
                                                               

</details>



# 答案4
**得分**: -2

欢迎来到StackOverflow。你的想法很不错，使用正则表达式是有道理的，但不幸的是这样不起作用。替换函数确实可以找到所有要替换的数字，但只能用一个值来替换它们。

一个可行的方法是逐个查找所有的数字，然后进行替换。这似乎是一个作业题，所以我不会提供实际的解决方案，你已经非常接近了！

<details>
<summary>英文:</summary>

welcome to StackOverflow. The idea you have is good, using regex makes sense, but won&#39;t work like that unfortunately. The replace function does find all of the numbers to replace, but can only replace them with one value.

One approach that would work is to find all of the numbers individually, then replace them. This seems like a homework assignment, so im not going to provide an actual solution and your already quite close by yourself!

</details>