How Can I Replace a Character at a Specific Index in an Immutable Java String?

Immutable Strings: Character Replacement at Specific Index

When dealing with strings in Java, one may encounter the need to replace a specific character at a particular index. However, unlike mutable data types, strings in Java are immutable, meaning they cannot be modified directly.

Consider the following code snippet:

String myName = "domanokz";
myName.charAt(4) = 'x'; // Throws an error

This code attempts to modify the character at index 4 in the myName string, but it results in an error because strings are immutable.

Solution: Creating a New String

To circumvent this, one must create a new string with the desired modification. This can be achieved using the substring method:

String myName = "domanokz";
String newName = myName.substring(0, 4) + 'x' + myName.substring(5);

The substring method extracts substrings from the original string based on specified indices. In this case, it creates two substrings: one from index 0 to index 4 (excluding index 4), and another from index 5 to the end of the string. These substrings are then concatenated with the desired character 'x' to form the new string, newName.

Alternative Solution: Using StringBuilder

Alternatively, one can use the StringBuilder class, which allows for the creation of mutable string representations. Here's an example:

StringBuilder myName = new StringBuilder("domanokz");
myName.setCharAt(4, 'x');

System.out.println(myName);

The StringBuilder class provides methods such as setCharAt that enable modifications to the underlying string representation. By using this class, one can avoid creating a new string each time a character replacement is needed. Once the modifications are complete, the toString method can be used to obtain the resulting string.

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