How to Split a String in Java

How do I split a string in Java?

Use the appropriately named method String#split().

String string = "004-034556";
String[] parts = string.split("-");
String part1 = parts[0]; // 004
String part2 = parts[1]; // 034556

Note that split's argument is assumed to be a regular expression, so remember to escape special characters if necessary.

there are 12 characters with special meanings: the backslash \, the caret ^, the dollar sign $, the period or dot ., the vertical bar or pipe symbol |, the question mark ?, the asterisk or star *, the plus sign +, the opening parenthesis (, the closing parenthesis ), and the opening square bracket [, the opening curly brace {, These special characters are often called "metacharacters".

For instance, to split on a period/dot . (which means "any character" in regex), use either backslash \ to escape the individual special character like so split("\\."), or use character class [] to represent literal character(s) like so split("[.]"), or use Pattern#quote() to escape the entire string like so split(Pattern.quote(".")).

String[] parts = string.split(Pattern.quote(".")); // Split on the exact string.

To test beforehand if the string contains certain character(s), just use String#contains().

if (string.contains("-")) {
    // Split it.
} else {
    throw new IllegalArgumentException("String " + string + " does not contain -");
}

Note, this does not take a regular expression. For that, use String#matches() instead.

If you'd like to retain the split character in the resulting parts, then make use of positive lookaround. In case you want to have the split character to end up in left hand side, use positive lookbehind by prefixing ?<= group on the pattern.

String string = "004-034556";
String[] parts = string.split("(?<=-)");
String part1 = parts[0]; // 004-
String part2 = parts[1]; // 034556

In case you want to have the split character to end up in right hand side, use positive lookahead by prefixing ?= group on the pattern.

String string = "004-034556";
String[] parts = string.split("(?=-)");
String part1 = parts[0]; // 004
String part2 = parts[1]; // -034556

If you'd like to limit the number of resulting parts, then you can supply the desired number as 2nd argument of split() method.

String string = "004-034556-42";
String[] parts = string.split("-", 2);
String part1 = parts[0]; // 004
String part2 = parts[1]; // 034556-42

Java String Split by |

You must use:

String [] temp = s.split("\\|");

This is because the split method takes a regular expression, and | is one of the special characters. It means 'or'. That means you are splitting by '' or '', which is just ''. Therefore it will split between every character.

You need two slashes because the first one is for escaping the actual \ in the string, since \ is Java's escape character in a string. Java understands the string like "\|", and the regex then understands it like "|".

Java string split with . (dot)

You need to escape the dot if you want to split on a literal dot:

String extensionRemoved = filename.split("\\.")[0];

Otherwise you are splitting on the regex ., which means "any character".

Note the double backslash needed to create a single backslash in the regex.

---

You're getting an ArrayIndexOutOfBoundsException because your input string is just a dot, ie ".", which is an edge case that produces an empty array when split on dot; split(regex) removes all trailing blanks from the result, but since splitting a dot on a dot leaves only two blanks, after trailing blanks are removed you're left with an empty array.

To avoid getting an ArrayIndexOutOfBoundsException for this edge case, use the overloaded version of split(regex, limit), which has a second parameter that is the size limit for the resulting array. When limit is negative, the behaviour of removing trailing blanks from the resulting array is disabled:

".".split("\\.", -1) // returns an array of two blanks, ie ["", ""]

ie, when filename is just a dot ".", calling filename.split("\\.", -1)[0] will return a blank, but calling filename.split("\\.")[0] will throw an ArrayIndexOutOfBoundsException.

Splitting string with pipe character (|)

| is a metacharacter in regex. You'd need to escape it:

String[] value_split = rat_values.split("\\|");

How to split a String by space

What you have should work. If, however, the spaces provided are defaulting to... something else? You can use the whitespace regex:

str = "Hello I'm your String";
String[] splited = str.split("\\s+");

This will cause any number of consecutive spaces to split your string into tokens.

Split a string at every 4-th character?

This ought to do it:

String[] split = myString.split("(?=(....)+$)");
// or
String[] split = myString.split("(?=(.{4})+$)");

What it does is this: split on the empty string only if that empty string has a multiple of 4 chars ahead of it until the end-of-input is reached.

Of course, this has a bad runtime (O(n^2)). You can get a linear running time algorithm by simply splitting it yourself.

As mentioned by @anubhava:

(?!^)(?=(?:.{4})+$) to avoid empty results if string length is in multiples of 4

How to split a string by every other separator

Using Regex

    String input = "ggg;ggg;nnn;nnn;aaa;aaa;xxx;xxx;";
    Pattern p = Pattern.compile("([a-z]{3});\\1;");
    Matcher m = p.matcher(input);
    while (m.find())
        // m.group(0) is the result
        System.out.println(m.group(0));

Will output

ggg;ggg;

nnn;nnn;

aaa;aaa;

xxx;xxx;

How to split a comma-separated string?

You could do this:

String str = "...";
List<String> elephantList = Arrays.asList(str.split(","));

Basically the .split() method will split the string according to (in this case) delimiter you are passing and will return an array of strings.

However, you seem to be after a List of Strings rather than an array, so the array must be turned into a list by using the Arrays.asList() utility. Just as an FYI you could also do something like so:

String str = "...";
ArrayList<String> elephantList = new ArrayList<>(Arrays.asList(str.split(","));

But it is usually better practice to program to an interface rather than to an actual concrete implementation, so I would recommend the 1st option.

---

Related Topics