如何从字符串中提取数字 [英] How to extract numbers from a string

问题描述

String a = "sin(23)+cos(4)+2!+3!+44!";
a.replaceAll("\D"); //Not working it is only extracting Digits 

我想提取<$ c的数字$ c>！仅限（示例 2 和 3 ），然后必须保存在 int [] 中，必须再次将这些数字粘贴到 2！和 3！存在。

I want to extract the numbers which are with ! only (example 2 and 3), then have to save it in a int[] and have to again paste those numbers at the place where 2! and 3! exist.

推荐答案

使用正则表达式找到你想要的东西：

Use regular expression to find what you want:

String a = "sin(23)+cos(4)+2!+3!+44!";

Pattern pattern = Pattern.compile("\\d+!"); //import java.util.regex.Pattern
Matcher matcher = pattern.matcher(a);       //import java.util.regex.Matcher
while (matcher.find()) {
    System.out.print("Start index: " + matcher.start());
    System.out.print(" End index: " + matcher.end() + " -> ");
    System.out.println(matcher.group());
}

输出：

Start index: 15 End index: 17 -> 2!
Start index: 18 End index: 20 -> 3!
Start index: 21 End index: 24 -> 44!

---

进一步改善：

使用以下内容，您可以使用<$ c $直接转换 matcher.group（1）返回值c> Integer.parseInt（）：

With the following, you can cast the matcher.group(1) return value directly using Integer.parseInt():

Pattern pattern = Pattern.compile("(\\d+)!");
...
    System.out.println(matcher.group(1));

输出：

Start index: 15 End index: 17 -> 2
Start index: 18 End index: 20 -> 3
Start index: 21 End index: 24 -> 44

---

你能弄清楚剩下的吗？您可以使用索引值替换原始字符串中的匹配项，但确保从最后一个字符串开始。

---

Can you figure out the rest? You could use the index values to replace the matches in the original string, but be sure to start from the last one.

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