How to prevent java.lang.String.split() from creating a leading empty string?

Question

passing 0 as a limit argument prevents trailing empty strings, but how does one prevent leading empty strings?

for instance

String[] test = "/Test/Stuff".split("/");

results in an array with "", "Test", "Stuff".

Yeah, I know I could roll my own Tokenizer... but the API docs for StringTokenizer say

"StringTokenizer is a legacy class that is retained for compatibility reasons although its use is discouraged in new code. It is recommended that anyone seeking this functionality use the split"

Answer 1

Your best bet is probably just to strip out any leading delimiter:

String input = "/Test/Stuff";
String[] test = input.replaceFirst("^/", "").split("/");

You can make it more generic by putting it in a method:

public String[] mySplit(final String input, final String delim)
{
    return input.replaceFirst("^" + delim, "").split(delim);
}

String[] test = mySplit("/Test/Stuff", "/");

Answer 2

Apache Commons has a utility method for exactly this: org.apache.commons.lang.StringUtils.split

StringUtils.split()

Actually in our company we now prefer using this method for splitting in all our projects.

Answer 3

I don't think there is a way you could do this with the built-in split method. So you have two options:

1) Make your own split

2) Iterate through the array after calling split and remove empty elements

If you make your own split you can just combine these two options

public List<String> split(String inString)
{
   List<String> outList = new ArrayList<>();
   String[]     test    = inString.split("/");

   for(String s : test)
   {
       if(s != null && s.length() > 0)
           outList.add(s);
   }

   return outList;
}

or you could just check for the delimiter being in the first position before you call split and ignore the first character if it does:

String   delimiter       = "/";
String   delimitedString = "/Test/Stuff";
String[] test;

if(delimitedString.startsWith(delimiter)){
    //start at the 1st character not the 0th
    test = delimitedString.substring(1).split(delimiter); 
}
else
    test = delimitedString.split(delimiter);

Answer 4

I think you shall have to manually remove the first empty string. A simple way to do that is this -

  String string, subString;
  int index;
  String[] test;

  string = "/Test/Stuff";
  index  = string.indexOf("/");
  subString = string.substring(index+1);

  test = subString.split("/"); 

This will exclude the leading empty string.

Answer 5

When using JDK8 and streams, just add a skip(1) after the split. Following sniped decodes a (very wired) hex encoded string.

Arrays.asList("\\x42\\x41\\x53\\x45\\x36\\x34".split("\\\\x"))
    .stream()
    .skip(1) // <- ignore the first empty element
    .map(c->""+(char)Integer.parseInt(c, 16))
    .collect(Collectors.joining())

Answer 6

Split method variants like split(regex, limit) can also produce empty strings at beginning or in middle of the resulting String array. Below code removes all such empty strings using streams api filter method in Java 8.

Sample code:

String[] tokens = s.split("/");
Arrays.stream(tokens)
.filter(s1 -> !s1.isEmpty())
.forEach(System.out::println);

Answer 7

I think there is no built-in function to remove blank string in Java. You can eliminate blank deleting string but it may lead to error. For safe you can do this by writing small piece of code as follow:

  List<String> list = new ArrayList<String>();

  for(String str : test) 
  {
     if(str != null && str.length() > 0) 
     {
         list.add(str);
     }
  }

  test = stringList.toArray(new String[list.size()]);

Answer 8

This is how I've gotten around this problem. I take the string, call .toCharArray() on it to split it into an array of chars, and then loop through that array and add it to my String list (wrapping each char with String.valueOf). I imagine there's some performance tradeoff but it seems like a readable solution. Hope this helps!

 char[] stringChars = string.toCharArray(); 
 List<String> stringList = new ArrayList<>(); 

 for (char stringChar : stringChars) { 
      stringList.add(String.valueOf(stringChar)); 
 }

Answer 9

You can use StringTokenizer for this purpose...

String test1 = "/Test/Stuff";
        StringTokenizer st = new StringTokenizer(test1,"/");
        while(st.hasMoreTokens())
            System.out.println(st.nextToken());

Answer 10

You can only add statement like if(StringUtils.isEmpty(string)) continue; before print the string. My JDK version 1.8, no Blank will be printed. 5 this program gives me problems