TheDeveloperBlog.com

Home | Contact Us

C-Sharp | Java | Python | Swift | GO | WPF | Ruby | Scala | F# | JavaScript | SQL | PHP | Angular | HTML

<< Back to JAVA

Java String Between, Before, After

Implement between, before and after methods to get substrings from strings. Simplify indexOf calls.
Between, before and after. Often we need to get a substring between two other substrings. The logic is simple, but a reusable method is helpful.Strings
IndexOf and substring. These methods locate the position of strings within a source string. With additional logic, we can take substrings relative to indexes.indexOfSubstring
Methods. This program introduces the between, before and after methods. For the three methods, the first argument is the String we are operating upon.

Between: This returns a possible substring between the second and third arguments (a and b). On failure, it returns an empty string.

Before: This is a simple method that returns the part of the string that occurs before the first index of the substring.

After: This does the opposite of the before() method. It is also simple and requires minimal logic.

Java program that implements between, before, after public class Program { static String between(String value, String a, String b) { // Return a substring between the two strings. int posA = value.indexOf(a); if (posA == -1) { return ""; } int posB = value.lastIndexOf(b); if (posB == -1) { return ""; } int adjustedPosA = posA + a.length(); if (adjustedPosA >= posB) { return ""; } return value.substring(adjustedPosA, posB); } static String before(String value, String a) { // Return substring containing all characters before a string. int posA = value.indexOf(a); if (posA == -1) { return ""; } return value.substring(0, posA); } static String after(String value, String a) { // Returns a substring containing all characters after a string. int posA = value.lastIndexOf(a); if (posA == -1) { return ""; } int adjustedPosA = posA + a.length(); if (adjustedPosA >= value.length()) { return ""; } return value.substring(adjustedPosA); } public static void main(String[] args) { // Test this string. final String test = "DEFINE:A=TWO"; // Call between, before and after methods. System.out.println(between(test, "DEFINE:", "=")); System.out.println(between(test, ":", "=")); System.out.println(before(test, ":")); System.out.println(before(test, "=")); System.out.println(after(test, ":")); System.out.println(after(test, "DEFINE:")); System.out.println(after(test, "=")); } } Output A A DEFINE DEFINE:A A=TWO A=TWO TWO
Tiny languages. With programs, domain-specific languages are often used for configuration files. With these methods, we can easily parse a DSL and extract parts from statements.

Define: In the main() method above, the string "DEFINE" could be used to set the variable A to the value TWO.

And: The between, before and after methods can be used to parse parts of this declarative statement.

In most tasks, performance is not the primary concern. For a configuration file language, one that is rarely run, correctness is more important.

And: These simple String methods help with writing correct code. The special value -1 is handled, avoiding possible exceptions.

One issue. These methods have a different behavior in a failure case. They will return an empty String, which may reduce exceptions but could cause incorrect behavior if not expected.
© TheDeveloperBlog.com
The Dev Codes

Related Links:


Related Links

Adjectives Ado Ai Android Angular Antonyms Apache Articles Asp Autocad Automata Aws Azure Basic Binary Bitcoin Blockchain C Cassandra Change Coa Computer Control Cpp Create Creating C-Sharp Cyber Daa Data Dbms Deletion Devops Difference Discrete Es6 Ethical Examples Features Firebase Flutter Fs Git Go Hbase History Hive Hiveql How Html Idioms Insertion Installing Ios Java Joomla Js Kafka Kali Laravel Logical Machine Matlab Matrix Mongodb Mysql One Opencv Oracle Ordering Os Pandas Php Pig Pl Postgresql Powershell Prepositions Program Python React Ruby Scala Selecting Selenium Sentence Seo Sharepoint Software Spellings Spotting Spring Sql Sqlite Sqoop Svn Swift Synonyms Talend Testng Types Uml Unity Vbnet Verbal Webdriver What Wpf