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How to split a string in Java


Question

I have a string, "004-034556", that I want to split into two strings:

string1="004";
string2="034556";

That means the first string will contain the characters before '-', and the second string will contain the characters after '-'. I also want to check if the string has '-' in it. If not, I will throw an exception. How can I do this?

2020/02/29
1
1667
2/29/2020 10:58:57 PM

Accepted Answer

Just use the appropriate method: String#split().

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

Note that this takes 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".

So, if you want to split on e.g. 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 period.

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
2017/08/02
2998
8/2/2017 12:34:46 PM

An alternative to processing the string directly would be to use a regular expression with capturing groups. This has the advantage that it makes it straightforward to imply more sophisticated constraints on the input. For example, the following splits the string into two parts, and ensures that both consist only of digits:

import java.util.regex.Pattern;
import java.util.regex.Matcher;

class SplitExample
{
    private static Pattern twopart = Pattern.compile("(\\d+)-(\\d+)");

    public static void checkString(String s)
    {
        Matcher m = twopart.matcher(s);
        if (m.matches()) {
            System.out.println(s + " matches; first part is " + m.group(1) +
                               ", second part is " + m.group(2) + ".");
        } else {
            System.out.println(s + " does not match.");
        }
    }

    public static void main(String[] args) {
        checkString("123-4567");
        checkString("foo-bar");
        checkString("123-");
        checkString("-4567");
        checkString("123-4567-890");
    }
}

As the pattern is fixed in this instance, it can be compiled in advance and stored as a static member (initialised at class load time in the example). The regular expression is:

(\d+)-(\d+)

The parentheses denote the capturing groups; the string that matched that part of the regexp can be accessed by the Match.group() method, as shown. The \d matches and single decimal digit, and the + means "match one or more of the previous expression). The - has no special meaning, so just matches that character in the input. Note that you need to double-escape the backslashes when writing this as a Java string. Some other examples:

([A-Z]+)-([A-Z]+)          // Each part consists of only capital letters 
([^-]+)-([^-]+)            // Each part consists of characters other than -
([A-Z]{2})-(\d+)           // The first part is exactly two capital letters,
                           // the second consists of digits
2017/07/17

String[] result = yourString.split("-");
if (result.length != 2) 
     throw new IllegalArgumentException("String not in correct format");

This will split your string into 2 parts. The first element in the array will be the part containing the stuff before the -, and the 2nd element in the array will contain the part of your string after the -.

If the array length is not 2, then the string was not in the format: string-string.

Check out the split() method in the String class.

https://docs.oracle.com/javase/8/docs/api/java/lang/String.html#split-java.lang.String-int-

2016/01/05

String[] out = string.split("-");

should do thing you want. String class has many method to operate with string.

2010/08/14

// This leaves the regexes issue out of question
// But we must remember that each character in the Delimiter String is treated
// like a single delimiter        

public static String[] SplitUsingTokenizer(String subject, String delimiters) {
   StringTokenizer strTkn = new StringTokenizer(subject, delimiters);
   ArrayList<String> arrLis = new ArrayList<String>(subject.length());

   while(strTkn.hasMoreTokens())
      arrLis.add(strTkn.nextToken());

   return arrLis.toArray(new String[0]);
}
2014/04/23

With Java 8:

    List<String> stringList = Pattern.compile("-")
            .splitAsStream("004-034556")
            .collect(Collectors.toList());

    stringList.forEach(s -> System.out.println(s));
2017/05/21

Source: https://stackoverflow.com/questions/3481828
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