I want to extract all substring that match regex pattern from a String and store them in a String array

Question

I want to extract all the substrings that have Exceptions. For example, "SQLException", "SQLSyntaxErrorException" etc from the below string, and store those values in a String array. How do I go about it? I tried to use the split(regex) method but that stores everything else in the array but not those exceptions. Help is appreciated.

public static void exceptionsOutOfString(){
    String input = "org.hibernate.exception.SQLException: error executing work org.hibernate.exception.SQLGrammarException: error \n" +
            "executing work &nbsp;&nbsp;&nbsp;&nbsp;at  ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final] &nbsp;&nbsp;&nbsp;&nbsp;\n" +
            "\\norg.hibernate.exception.SQLGrammarException: error executing work &nbsp;&nbsp;&nbsp;&nbsp;at  ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final] \n" +
            "&nbsp;&nbsp;&nbsp;&nbsp; Caused by: java.sql.SQLSyntaxErrorException: malformed string: 'Acme''&nbsp;&nbsp;&nbsp;&nbsp;at";

    String regex = ".[a-zA-Z]*Exception";

    String[] exceptions  = input.split(regex);

Please show exactly what strings you expect to capture

alotropico
– alotropico

2020-07-24 22:54:21 +00:00
Commented Jul 24, 2020 at 22:54 — alotropico
– alotropico, Commented Jul 24, 2020 at 22:54

WJS · Accepted Answer · 2020-07-26 14:42:50Z

2

Try this:

String input = <exception list...>
String regex = "\\w+Exception";
Matcher m = Pattern.compile(regex).matcher(input);

while (m.find()) {
    System.out.println(m.group());
}

Prints

SQLException
SQLGrammarException
SQLGrammarException
SQLSyntaxErrorException

To put them in an array, do the following:

String[] array = m.results()
             .map(MatchResult::group)
             .toArray(String[]::new);

m.results() produces a stream of MatchResults. So take that and use the group method to get the string then return an array.

As was astutely observed by Abra, the above was not introduced until release JDK 9.

Here is an alternative.

List<String> list = new ArrayList<>();
while (m.find()) {
     list.add(m.group());
}

Then either use as a list or convert.

String[] array = list.stream().toArray(String[]::new);
// or
String[] array = list.toArray(String[]::new); // JDK 11

edited Jul 26, 2020 at 14:42

answered Jul 25, 2020 at 0:33

WJS

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3 Comments

breadfan18 Over a year ago

Thanks. How do i put the results of the matcher in a String[] array?

Abra Over a year ago

Perhaps you should mention that method results() was added to class Matcher in JDK 9?

breadfan18 Over a year ago

Thanks @WJS that works. Thanks for your help!! I was asked this question and the guy had a one line solution for extracting the regex matches from the string and store them in an array. I just can't remember what he did! :(

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