String management, functions for working with strings in Java

In this tutorial we will continue learning about strings in Java. The basics of working with strings can be found in the lesson “Strings in Java”. A class Stringin Java has a set of methods for manipulating the contents of a string. Find characters, substrings, change case and other tasks.

Getting characters and substrings

You can get the character that is at a specific position in a string by calling the charAt(). The index of the first character in the line is 0, the last one is length()-1. The following code returns the 9th character of the string.

String anotherPalindrome = "Niagara. O roar again!";
char aChar = anotherPalindrome.charAt(9);

The numbering of characters starts from 0, so the 9th character in the line is “O”. If you need to get not just one character, but part of a string, you can use the substring. The method substringhas two options: The following code will return a substring of the string, starting from the 11th character, but not including the 15th, resulting in the word “roar”

String anotherPalindrome = "Niagara. O roar again!";
String roar = anotherPalindrome.substring(11, 15);

Other methods for manipulating strings

The table shows some methods for working with strings and their descriptions.

Search for characters and substrings

Let's look at a few more methods for searching for characters and substrings. The class Stringcontains methods that return the position of a character or substring in a string: indexOf()and lastIndexOf(). The methods indexOf()search from the beginning of the string, lastIndexOf()from the end. If these methods do not find a match, they return -1. The class also Stringcontains a method containsthat returns true if the specified sequence of characters is contained in the string. Use this method if you need to know whether a substring exists in a string, but its position is not important. The following table describes the indexOf()and methods lastIndexOf(). CharSequenceis an interface that the class implements String, so you can pass strings to the contains().

Changing lines. Replacing characters and substrings

The class Stringhas several methods for inserting characters and substrings into a string. The table describes methods for replacing found characters and substrings.

Example

The following class Filenameshows an example of using the lastIndexOf()and methods substring()to use different parts of a string with a file name. Now consider a program that uses the class Filename: The program will output: The method extensionuses a method lastIndexOfto determine the last occurrence of " .". The method substringuses this value to find the file extension. Link to the original source: String management, functions for working with strings in Java String management, functions for working with strings in Java. Part 2