Trim String in Java, keeping the full word

Question

I need to trim a string in java so that:

A quick brown fox jumps over a dog-manhole.

becomes

Quick brown ...

In the above example, I truncate to 12 characters. If I just use a substring, I would get:

Quick ...

I already have a method for this, using a substring, but I wanted to know what is the fastest (most efficient) way to do this, because a page can have many trim operations.

The only way I can think of is to split the string into spaces and put it back together until its length has passed the given length. Is there another way? Perhaps in a more efficient way that I can use the same method for soft trim, where I save the last word (as shown in the example above) and hard trim, which is pretty much a substring.

Thanks,

Answer 1

Below is the method that I use to trim long lines in my web folders. The soft boolean , as you put it, if set to true , the last word will be saved. This is the most concise way to do this so that I can come up with what uses a StringBuffer, which is much more efficient than re-creating a string that is immutable.

 public static String trimString(String string, int length, boolean soft) { if(string == null || string.trim().isEmpty()){ return string; } StringBuffer sb = new StringBuffer(string); int actualLength = length - 3; if(sb.length() > actualLength){ // -3 because we add 3 dots at the end. Returned string length has to be length including the dots. if(!soft) return escapeHtml(sb.insert(actualLength, "...").substring(0, actualLength+3)); else { int endIndex = sb.indexOf(" ",actualLength); return escapeHtml(sb.insert(endIndex,"...").substring(0, endIndex+3)); } } return string; } 

Update

I changed the code so that ... was added to the StringBuffer to prevent unnecessary String creation implicitly, which is slow and wasteful.

Note. escapeHtml is a static import from apache commons:

import static org.apache.commons.lang.StringEscapeUtils.escapeHtml;

You can remove it, and the code should work the same.

Answer 2

Here is a simple, regex-based, single-line solution:

 str.replaceAll("(?<=.{12})\\b.*", "..."); // How easy was that!? :) 

Explanation:

• (?<=.{12}) is a negative appearance that states that at least 12 characters remain to the left of the match, but it is a non-convertible (i.e. null) match
• \b.* matches the first word boundary (after at least 12 characters - above) to the end

This is replaced by "..."

Here's the test:

 public static void main(String[] args) { String input = "The quick brown fox jumps over the lazy dog."; String trimmed = input.replaceAll("(?<=.{12})\\b.*", "..."); System.out.println(trimmed); } 

Output:

 The quick brown... 

Answer 3

Please try the following code:

 private String trim(String src, int size) { if (src.length() <= size) return src; int pos = src.lastIndexOf(" ", size - 3); if (pos < 0) return src.substring(0, size); return src.substring(0, pos) + "..."; } 

Answer 4

Try to find the last place in the space that is at a position of less than or greater than 11 and cuts the line there by adding "...".

Answer 5

Your requirements are not clear. If you have problems formulating them in a natural language, it is not surprising that it will be difficult for them to translate into a computer language such as Java.

“save last word” means that the algorithm will know what the word is, so you should say that first. Splitting is the way to do it. A grammar scanner / parser is another.

I will worry about making it work before I take care of myself. Make it work, measure it, and then see what you can do with performance. Everything else is speculation without data.

Answer 6

What about:

 mystring = mystring.replaceAll("^(.{12}.*?)\b.*$", "$1..."); 

Answer 7

I use this hack: suppose the cropped string should be 120:

 String textToDisplay = textToTrim.substring(0,(textToTrim.length() > 120) ? 120 : textToTrim.length()); if (textToDisplay.lastIndexOf(' ') != textToDisplay.length() &&textToDisplay.length()!=textToTrim().length()) { textToDisplay = textToDisplay + textToTrim.substring(textToDisplay.length(),textToTrim.indexOf(" ", textToDisplay.length()-1))+ " ..."; }