在Java中向前或向后从空格或制表符修剪

Question

I know how to trim things in Java but how does one trim from a space or tab to the left or to the right? I have a program that searches for some 4 character prefixes let's say this prefix is XYBC then it has X amount of characters to it like XYBC4975723434 but the line that my code takes looks like this:

Viuhaskfdksjfkds XYBC4975723434 fkdsjkfjaksjfklsdakldjsen

But then I would like it to trim it to this: XYBC4975723434 Thanks

Answer 1

That is not a trim, but a regular expression find, using the following regex:

\bXYBC.*?\b

That expression used word boundaries, which may not be what you want.

For whitespace, use:

(?<=^|\s)XYBC\S*

Test

public static void main(String[] args) {
    test("Viuhaskfdksjfkds  XYBC4975723434 fkdsjkfjaksjfklsdakldjsen");
    test("XYBC4975723434");
    test("Viuhaskfdksjfkds  xXYBC4975723434 fkdsjkfjaksjfklsdakldjsen");
    test("abc XYBC49-75(723)4$34 xyz");
}
private static void test(String text) {
    Matcher m = Pattern.compile("\\bXYBC.*?\\b").matcher(text);
    if (m.find()) {
        System.out.println(m.group());
    } else {
        System.out.println("Not found: " + text);
    }
}

Output (word boundary)

XYBC4975723434
XYBC4975723434
Not found: Viuhaskfdksjfkds  xXYBC4975723434 fkdsjkfjaksjfklsdakldjsen
XYBC49

Output (whitespace)

XYBC4975723434
XYBC4975723434
Not found: Viuhaskfdksjfkds  xXYBC4975723434 fkdsjkfjaksjfklsdakldjsen
XYBC49-75(723)4$34

Answer 2

I have a prog that searches for some 4 character prefixes let's say this prefix is XYBC then it has X amount of characters to it

If you want your program to grab a substring with specific starting letters and grab a specific number of letters, you may do this (apart from using regular expression):

public static String grabText(String str, String find, int n){
    int idx = str.indexOf(find);    
    if(idx == -1)
        return "";
    else{
       String sub = str.substring(idx, Math.min(n, str.length() - idx)+ idx);
        return sub; 
    }
}

TEST:

String str = "Viuhaskfdksjfkds  XYBC4975723434 fkdsjkfjaksjfklsdakldjsen";
System.out.println(grabText(str, "XYBC", 14));
System.out.println(grabText(str, "XYBC", 5));           
System.out.println(grabText(str, "XYBC", 100)); 
System.out.println(grabText(str, "XYBC", 9999));    

OUTPUT:

XYBC4975723434
XYBC4
XYBC4975723434 fkdsjkfjaksjfklsdakldjsen
XYBC4975723434 fkdsjkfjaksjfklsdakldjsen

Answer 3

You can use regular expressions to achieve this. For example, by using the regular expression XYBC\\d+ , you can match or find any sequence of numbers which are prefixed with XYBC . In code, that would look like this:

String input = "Viuhaskfdksjfkds  XYBC4975723434 fkdsjkfjaksjfklsdakldjsen";
Pattern pattern = Pattern.compile("XYBC\\d+");
Matcher matcher = pattern.matcher(input);

if (!matcher.find()) throw new RuntimeException("failed to find any numbers prefixed with XYBC!");

System.out.println(matcher.group()); // prints "XYBC4975723434"

Also check out the details of the given regular expression here .