JAVA – Inserting a new line at the next space after 30 characters

javanewlinestring

I have a large block of text (200+ characters in a String) and need to insert new lines at the next space after 30 characters, to preserve words. Here is what I have now (NOT working):

String rawInfo = front.getItemInfo(name);
String info = "";
int begin = 0;
for(int l=30;(l+30)<rawInfo.length();l+=30) {
    while(rawInfo.charAt(l)!=' ')
        l++;
    info += rawInfo.substring(begin, l) + "\n";
    begin = l+1;
    if((l+30)>=(rawInfo.length()))
        info += rawInfo.substring(begin, rawInfo.length());
}

Thanks for any help

Best Solution

As suggested by kdgregory, using a StringBuilder would probably be an easier way to work with string manipulation.

Since I wasn't quite sure if the number of characters before the newline is inserted is the word before or after 30 characters, I opted to go for the word after 30 characters, as the implementation is probably easier.

The approach is to find the instance of the " " which occurs at least 30 characters after the current character which is being viewed by using StringBuilder.indexOf. When a space occurs, a \n is inserted by StringBuilder.insert.

(We'll assume that a newline is \n here -- the actual line separator used in the current environment can be retrieved by System.getProperty("line.separator");).

Here's the example:

String s = "A very long string containing " +
    "many many words and characters. " +
    "Newlines will be entered at spaces.";

StringBuilder sb = new StringBuilder(s);

int i = 0;
while ((i = sb.indexOf(" ", i + 30)) != -1) {
    sb.replace(i, i + 1, "\n");
}

System.out.println(sb.toString());

Result:

A very long string containing many
many words and characters. Newlines
will.

I should add that the code above hasn't been tested out, except for the example String that I've shown in the code. It wouldn't be too surprising if it didn't work under certain circumstances.

Edit

The loop in the sample code has been replaced by a while loop rather than a for loop which wasn't very appropriate in this example.

Also, the StringBuilder.insert method was replaced by the StringBuilder.replace method, as Kevin Stich mentioned in the comments that the replace method was used rather than the insert to get the desired behavior.

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Java – What are the differences between a HashMap and a Hashtable in Java

There are several differences between HashMap and Hashtable in Java:

Hashtable is synchronized, whereas HashMap is not. This makes HashMap better for non-threaded applications, as unsynchronized Objects typically perform better than synchronized ones.
Hashtable does not allow null keys or values. HashMap allows one null key and any number of null values.
One of HashMap's subclasses is LinkedHashMap, so in the event that you'd want predictable iteration order (which is insertion order by default), you could easily swap out the HashMap for a LinkedHashMap. This wouldn't be as easy if you were using Hashtable.

Since synchronization is not an issue for you, I'd recommend HashMap. If synchronization becomes an issue, you may also look at ConcurrentHashMap.

Php – How to Truncate a string in PHP to the word closest to a certain number of characters

By using the wordwrap function. It splits the texts in multiple lines such that the maximum width is the one you specified, breaking at word boundaries. After splitting, you simply take the first line:

substr($string, 0, strpos(wordwrap($string, $your_desired_width), "\n"));

One thing this oneliner doesn't handle is the case when the text itself is shorter than the desired width. To handle this edge-case, one should do something like:

if (strlen($string) > $your_desired_width) 
{
    $string = wordwrap($string, $your_desired_width);
    $string = substr($string, 0, strpos($string, "\n"));
}

The above solution has the problem of prematurely cutting the text if it contains a newline before the actual cutpoint. Here a version which solves this problem:

function tokenTruncate($string, $your_desired_width) {
  $parts = preg_split('/([\s\n\r]+)/', $string, null, PREG_SPLIT_DELIM_CAPTURE);
  $parts_count = count($parts);

  $length = 0;
  $last_part = 0;
  for (; $last_part < $parts_count; ++$last_part) {
    $length += strlen($parts[$last_part]);
    if ($length > $your_desired_width) { break; }
  }

  return implode(array_slice($parts, 0, $last_part));
}

Also, here is the PHPUnit testclass used to test the implementation:

class TokenTruncateTest extends PHPUnit_Framework_TestCase {
  public function testBasic() {
    $this->assertEquals("1 3 5 7 9 ",
      tokenTruncate("1 3 5 7 9 11 14", 10));
  }

  public function testEmptyString() {
    $this->assertEquals("",
      tokenTruncate("", 10));
  }

  public function testShortString() {
    $this->assertEquals("1 3",
      tokenTruncate("1 3", 10));
  }

  public function testStringTooLong() {
    $this->assertEquals("",
      tokenTruncate("toooooooooooolooooong", 10));
  }

  public function testContainingNewline() {
    $this->assertEquals("1 3\n5 7 9 ",
      tokenTruncate("1 3\n5 7 9 11 14", 10));
  }
}

EDIT :

Special UTF8 characters like 'à' are not handled. Add 'u' at the end of the REGEX to handle it:

$parts = preg_split('/([\s\n\r]+)/u', $string, null, PREG_SPLIT_DELIM_CAPTURE);

Best Solution

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EDIT :

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