Languages
[Edit]
EN

Java - replace first character in string

0 points
Created by:
Zachariah
298

In this article, we would like to show you how to replace the first character in string in Java.

Quick solution:

String text = "ABC";
String replacement = "x";
String result = replacement + text.substring(1);

System.out.println(result);  // xBC

or:

String text = "ABC";
String replacement = "x";
String result = replacement.concat(text.substring(1));

System.out.println(result);  // xBC

or:

String text = "ABC";
String replacement = "x";
String result = text.replaceAll("^.", replacement);

System.out.println(result);  // xBC

 

1. Practical example using String substring()

1.1 With + operator

In this example, we remove last character from the original string and add the replacement at the beginning.

public class Example {

    public static void main(String[] args) {
        String text = "ABC";
        String replacement = "x";
        String result = replacement + text.substring(1);

        System.out.println(result);  // xBC
    }
}

1.2 With concat() method

This approach is equivalent to the above one. Instead of + operator we concatenate the strings using concat() method.

public class Example {

    public static void main(String[] args) {
        String text = "ABC";
        String replacement = "x";
        String result = replacement.concat(text.substring(1));

        System.out.println(result);  // xBC
    }
}

2. Practical example using String replaceAll() with regex pattern

In this example, we use string replaceAll() with "^." regex to replace the first character in the text string.

Regex explanation:

  • ^ - matches the beginning of the string,
  • . - matches any character except linebreaks.
public class Example {

    public static void main(String[] args) {
        String text = "ABC";
        String replacement = "x";
        String result = text.replaceAll("^.", replacement);

        System.out.println(result);  // xBC
    }
}

Note:

Regular expressions are slower than substring() method. 

Donate to Dirask
Our content is created by volunteers - like Wikipedia. If you think, the things we do are good, donate us. Thanks!
Join to our subscribers to be up to date with content, news and offers.

Java - String (popular problems)

Java - replace first character in string
Native Advertising
🚀
Get your tech brand or product in front of software developers.
For more information Contact us
Dirask - we help you to
solve coding problems.
Ask question.

❤️💻 🙂

Join