Removing all characters but letters in a string

问题

If I have a string "ja.v_,a", how can I remove all non-letter characters to output "java"? I have tried str = str.replaceAll("\\W", "" ), but to no avail.

回答1:

Could you try this one?

System.out.println("ja.v_,a".replaceAll("[^a-zA-Z]", "")) //java

回答2:

I would like to refer to this article and quote it:

Regex examples and tutorials always give you the [a-zA-Z0-9]+ regex to "validate alphanumeric input". It is built-in in many validation frameworks. And it is so utterly wrong. This is a regex that must never appear anywhere in your code, unless you have a pretty good explanation. Yet, the example is ubiquitous. Instead, the right regex is [\p{L}0-9]+

So in your case it would be:

str.replaceAll("[^\\p{L}]", "");
System.out.println("ja.v_,a".replaceAll("[^\\p{L}]", ""));
System.out.println("сл-=о-_=во!".replaceAll("[^\\p{L}]", ""));

Where \p{L} is the Unicode definition of a "letter".

回答3:

String test= "ja.v_,a";

int len=test.length();

String alphaString="";

for(int i=0; i<len; i++){
     if (Character.isLetter(test.charAt(i))) {
         alphaString=alphaString+test.charAt(i);
     }
}

System.out.println(alphaString);

回答4:

String s = "ja.v_,a";
s = s.replaceAll("[^a-z]", "");
System.out.println(s);

>java

来源：https://stackoverflow.com/questions/43263680/removing-all-characters-but-letters-in-a-string