Using the find method and start method of the Matcher class, we can implement our own indexOf method that accepts a regex pattern as given below. In that case, we can use the Pattern and Matcher class. You can replace 7 with any number say N, if you want to get last 'N' characters. In this case, the indexOf method of the String class cannot be used. You can achieve it using this single line code : String numbers text.substring (text.length () - 7, text.length ()) But be sure to catch Exception if the input string length is less than 7. With parameters 6 and 11, the str string is passed to the substring () method. It gives back a brand-new string that contains all of the characters from the starting index (inclusive) all the way to the ending index (exclusive) of the original string. For example, you want to find an index of a number in the string, but you do not know the exact number you are looking for. A section of a string can be extracted using the Java substring (begIndex, endIndex) function. The indexOf method of the String class does not accept a regex pattern. However, many times some use case requires us to search for a complicated pattern inside of the string content instead of a simple substring. A String in Java is actually an object, which contain methods that can perform certain operations on strings. These indexOf methods are overloaded for String as well char data types. That’s where the Java substring() method comes in. The Java String class provides overloaded indexOf methods to find the index of a specific substring or subsequence within given string content. How to find the index of a substring using regex in Java? Java RegEx – indexOf & lastIndexOf substring example shows how to find an index of a substring in a string using regular expression pattern instead of indexOf or lastIndexOf methods of the String class.
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