![\"\"](\"https:\/\/www.baeldung.com\/wp-content\/uploads\/2021\/09\/Java-4-Featured-1024x536.png\")
<\/p>\n<\/p>\n
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When we code in Java, there are many scenarios where we need to extract text enclosed within parentheses. Understanding how to retrieve the text between parentheses is an essential skill.<\/p>\n
In this tutorial, we’ll explore different methods to achieve this, focusing on regular expressions<\/a> and some popular external libraries.<\/p>\n When our input contains only one pair of parentheses, we can extract the content between them using two replaceAll()<\/em><\/a> method calls:<\/p>\n As the example above shows, the first replaceAll()<\/em> removes everything until the ‘(<\/em>‘ character. The second replaceAll()<\/em> removes from ‘)<\/em>‘ until the end of the String<\/em>.\u00a0<\/strong>Thus, the rest is the text between ‘(<\/em>‘ and ‘)<\/em>‘.<\/p>\n However, this approach won’t work if our input has multiple “(…)” pairs. For example, let’s say we have another input:<\/p>\n There are three pairs of parentheses in INPUT<\/em>. Therefore, we expect to see extracted values in the following String List<\/em>:<\/p>\n Next, let’s see how to extract these String<\/em> values from the INPUT String<\/em>.<\/p>\n For simplicity, we’ll leverage unit test assertions to verify whether each approach works as expected.<\/p>\n Regular expressions (regex) provide a powerful and flexible method for pattern matching and text extraction. So, let’s use regex to do the job.<\/p>\n Some of us may come up with this pattern to extract text between ‘(‘ and ‘)’: “[(](.*)[)]<\/em>“. This pattern is pretty straightforward:<\/p>\n Next, let’s check if this pattern solves the problem correctly:<\/p>\n As the above test shows, using this pattern, we only have one String<\/em> element in the result List<\/em>: “b c) d (e f) x (y z”.\u00a0<\/em>This is because the ‘*’ quantifier<\/a> applies a greedy match.\u00a0<\/strong>In other words, “[(](.*)[)]<\/em>” matches the first ‘(‘ in the input and then everything up to the last ‘)’ character, even if the content includes other “(…)” pairs<\/strong>.<\/b><\/p>\n This isn’t what we expected. To solve the problem, we need non-greedy matching, which means the pattern must match each “(…)” pair.<\/p>\n To make the ‘*’ quantifier non-greedy, we can add a question mark ‘?’ after it: “[(](*?)[)]<\/em>“.<\/strong><\/p>\n Next, let’s test if this pattern can extract the expected String<\/em> elements:<\/p>\n As we can see, the non-greedy regex pattern “[(](.*?)[)]<\/em>” does the job.<\/p>\n Apart from using the non-greedy quantifier (*?<\/em>), we can also solve the problem using regex’s negated character class<\/strong>:<\/p>\n As the code shows, our regex pattern to extract texts between parentheses is “[(]([^)]*)<\/em>“. Let’s break it down to understand how it works:<\/p>\n Alternatively, we can replace the “[(]<\/em>”\u00a0character class with a positive lookbehind<\/a> assertion “(?<=[(])<\/em>“. Lookbehind assertions allow us to match a group of characters only if a specified pattern precedes them.<\/strong> In this example, (?<=[(])<\/em> asserts that what immediately precedes the current position is an opening parenthesis ‘(‘:<\/p>\n It’s worth noting that since lookaround<\/a> is a zero-width assertion, the ‘(‘ character won’t be captured<\/strong>. Thus, we don’t need to create a capturing group to extract the expected text.<\/p>\n Apache Commons Lang 3<\/a> is a widely used library. Its StringUtils<\/em><\/a> class offers a rich set of convenient methods for manipulating String<\/em> values.<\/p>\n If we have only one pair of parentheses in the input, the StringUtils.substringBetween()<\/em> method allows us to extract the String<\/em> between them straightforwardly<\/strong>:<\/p>\n When the input has multiple pairs of parentheses, StringUtils.substringsBetween()\u00a0<\/em>returns texts inside parentheses pairs in an array<\/strong>:<\/p>\n If we’re using the Apache Commons Lang 3 library already in our project, these two methods are good choices for this task.<\/p>\n In this article, we’ve explored different ways to extract text between parentheses in Java. By understanding and applying these techniques, we can efficiently parse and process text in our Java applications.<\/p>\n As always, the complete source code for the examples is available over on GitHub<\/a>.<\/p>\n Learn how to use regular expressions to extract text between parentheses in Java.<\/p>\n2. Introduction to the Problem<\/h2>\n
<\/div>\nString myString = "a b c (d e f) x y z";\r\n \r\nString result = myString.replaceAll(".*[(]", "")\r\n .replaceAll("[)].*", "");\r\nassertEquals("d e f", result);<\/code><\/pre>\nstatic final String INPUT = "a (b c) d (e f) x (y z)";<\/code><\/pre>\nstatic final List<String> EXPECTED = List.of("b c", "e f", "y z");<\/code><\/pre>\n3. Greedy vs Non-greedy Regex Pattern<\/h2>\n
<\/div>\n\n
String myRegex = "[(](.*)[)]";\r\nMatcher myMatcher = Pattern.compile(myRegex)\r\n .matcher(INPUT);\r\nList<String> myResult = new ArrayList<>();\r\nwhile (myMatcher.find()) {\r\n myResult.add(myMatcher.group(1));\r\n}\r\nassertEquals(List.of("b c) d (e f) x (y z"), myResult);<\/code><\/pre>\nString regex = "[(](.*?)[)]";\r\nList<String> result = new ArrayList<>();\r\nMatcher matcher = Pattern.compile(regex)\r\n .matcher(INPUT);\r\nwhile (matcher.find()) {\r\n result.add(matcher.group(1));\r\n}\r\nassertEquals(EXPECTED, result);<\/code><\/pre>\n4. Using the Negated Character Class<\/h2>\n
<\/div>\nString regex = "[(]([^)]*)";\r\nList<String> result = new ArrayList<>();\r\nMatcher matcher = Pattern.compile(regex)\r\n .matcher(INPUT);\r\nwhile (matcher.find()) {\r\n result.add(matcher.group(1));\r\n}\r\nassertEquals(EXPECTED, result);<\/code><\/pre>\n\n
String regex = "(?<=[(])[^)]*";\r\nList<String> result = new ArrayList<>();\r\nMatcher matcher = Pattern.compile(regex)\r\n .matcher(INPUT);\r\nwhile (matcher.find()) {\r\n result.add(matcher.group());\r\n}\r\nassertEquals(EXPECTED, result);<\/code><\/pre>\n5. Using StringUtils<\/em> From Apache Commons Lang 3<\/h2>\n
<\/div>\nString myString = "a b c (d e f) x y z";\r\n \r\nString result = StringUtils.substringBetween(myString, "(", ")");\r\nassertEquals("d e f", result);<\/code><\/pre>\nString[] results = StringUtils.substringsBetween(INPUT, "(", ")");\r\nassertArrayEquals(EXPECTED.toArray(), results);<\/code><\/pre>\n6. Conclusion<\/h2>\n
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