[英]Case-insensitive string matching in Java without anchors
NOTE : This is NOT a question about case-insensitive matching. 注意 :这不是关于不区分大小写匹配的问题。 It is a question about
regex
anchors. 这是关于
regex
锚点的问题。
I'm having a lot of trouble doing basic case insensitive matching in Java: 我在Java中进行基本的不区分大小写的匹配时遇到了很多麻烦:
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class match {
public static void main(String[] args) {
String prompt="das101.lo1>";
String str="automate@DAS101.LO1>";
Pattern ignore = Pattern.compile(prompt.toUpperCase(), Pattern.CASE_INSENSITIVE);
Matcher mIgn = ignore.matcher(str);
if(mIgn.matches())
System.out.println(str+" Matches " + prompt.toUpperCase());
else
System.out.println(str+" Doesn't Match " + prompt.toUpperCase());
char[] cStr = str.toCharArray();
char[] cPrompt = prompt.toUpperCase().toCharArray();
/* Verify that strings match */
for(int i=cPrompt.length-1, j=cStr.length-1; i>=0 && j>=0 ; --i,--j) {
if (cPrompt[i]==cStr[j])
System.out.println("Same: "+ cPrompt[i]+":" + cStr[j]);
else
System.out.println("Different: "+ cPrompt[i]+":" + cStr[j]);
}
}
}
The output: 输出:
samveen@javadev-tahr:/tmp$ javac match.java
samveen@javadev-tahr:/tmp$ java match
automate@DAS101.LO1> Doesn't Match DAS101.LO1>
Same: >:>
Same: 1:1
Same: O:O
Same: L:L
Same: .:.
Same: 1:1
Same: 0:0
Same: 1:1
Same: S:S
Same: A:A
Same: D:D
If I change if(mIgn.matches())
to if(mIgn.find())
, I get this simple string pattern match working: 如果我将
if(mIgn.matches())
更改为if(mIgn.find())
,我会得到这个简单的字符串模式匹配工作:
samveen@javadev-tahr:/tmp$ javac match.java
samveen@javadev-tahr:/tmp$ java match
automate@DAS101.LO1> Matches DAS101.LO1>
Same: >:>
Same: 1:1
Same: O:O
Same: L:L
Same: .:.
Same: 1:1
Same: 0:0
Same: 1:1
Same: S:S
Same: A:A
Same: D:D
Where am I going wrong? 我哪里错了?
I referred to Case-Insensitive Matching in Java RegEx and Methods of the Pattern Class 我提到了Java RegEx中的Case-Insensitive Matching和Pattern Class的方法
String.matches
requires the entire string to match the pattern. String.matches
需要整个字符串匹配模式。 As if the pattern has an implied "^...$". 好像模式有隐含的“^ ... $”。
Pattern ignore = Pattern.compile(".*" + Pattern.quote(prompt) + ".*",
Pattern.CASE_INSENSITIVE);
is for a find like match. 是为了寻找匹配。
This could have been done with the original pattern as: 这可以使用原始模式完成:
if (mIgn.find()) {
System.out.println("Found at position " + mIgn.start());
}
Matches return true if the whole string matches the given pattern. 如果整个字符串与给定模式匹配,则匹配返回true。 For this it prefix ur matcher with '^' and suffix with '$' sign and hence it is not going to look for a substring.
为此,它为ur匹配前缀为'^',后缀为'$'符号,因此它不会查找子字符串。
find() return true in case of substring matches also. find()在子串匹配的情况下也返回true。
Have a look - Difference between matches() and find() in Java Regex 看看 - Java Regex中的matches()和find()之间的区别
matches()
only returns true
if the whole input matches the pattern, not if part of the input matches the pattern. matches()
仅在整个输入与模式匹配时才返回true
,而不是在输入的一部分与模式匹配时返回true
。
The input automate@DAS101.LO1>
does not match the complete pattern das101.lo1>
. 输入
automate@DAS101.LO1>
与完整模式das101.lo1>
不匹配。
That explains the different result you get when you use find()
instead of matches()
. 这解释了使用
find()
而不是matches()
时得到的不同结果。
Use ?i
regex with .matches
for case insensitive matching: 使用
?i
regex和.matches
进行不区分大小写的匹配:
// ?i = case insensitive match
if (mIgn.matches("(?i:str)")) {
......
} else {
......
}
Use this Utility method for case-insensitive matches 将此实用程序方法用于不区分大小写的匹配项
// utlity method for mathcesIgonerCase
public static boolean mathcesIgonerCase(String string1, String sentence){
return string1.matches("(?i:.*"+sentence+".*)");
}
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