2019-11-02 12:07:41 +08:00
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# 20. 表示数值的字符串
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2021-03-23 02:48:19 +08:00
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[牛客网](https://www.nowcoder.com/practice/e69148f8528c4039ad89bb2546fd4ff8?tpId=13&tqId=11206&tab=answerKey&from=cyc_github)
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2019-11-02 12:07:41 +08:00
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## 题目描述
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```
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true
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"+100"
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"5e2"
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"-123"
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"3.1416"
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"-1E-16"
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```
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```
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false
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"12e"
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"1a3.14"
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"1.2.3"
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"+-5"
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"12e+4.3"
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```
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## 解题思路
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使用正则表达式进行匹配。
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```html
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[] ： 字符集合
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() ： 分组
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? ： 重复 0 ~ 1 次
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+ ： 重复 1 ~ n 次
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* ： 重复 0 ~ n 次
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. ： 任意字符
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\\. ： 转义后的 .
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\\d ： 数字
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```
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```java
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2021-03-23 02:48:19 +08:00
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public boolean isNumeric (String str) {
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if (str == null || str.length() == 0)
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2019-11-02 12:07:41 +08:00
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return false;
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return new String(str).matches("[+-]?\\d*(\\.\\d+)?([eE][+-]?\\d+)?");
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}
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```
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