Replace Character in String in Java

  1. String.replace() to Replace a Single Character in a Java String
  2. String.replaceFirst() to Replace Only the First Occurrence of a Character in a Java String
  3. String.replace() to Replace Two Characters in a String in Java

In this tutorial, we will introduce two methods, replace() and replaceFirst() of the String class, replacing one or more characters in a given string in Java.

String.replace() to Replace a Single Character in a Java String

We can use the replace() method to replace a single character in a string. replace(oldChar, newChar) demands two arguments: the first argument is the character that we want to be replaced, and the second argument is a new character that is to replace the old character.

In the following example, we have a string oldString1 containing a statement with an &, but we want to replace it with a coma. This can be simply done by calling the replace() method using oldString1 and passing & and a coma.

One important thing to notice here is that there is whitespace before & in replace(). It is because there is whitespace around our target character. To eliminate the whitespace, we will replace both & and the whitespace with coma.

public class ReplaceCharString {
    public static void main(String[] args) {

        String oldString1 = "My name is Sam & I am a software developer.";

        String newString1 = oldString1.replace(" &", ",");

        System.out.println(newString1);

    }
}

Output:

My name is Sam, I am a software developer.

String.replaceFirst() to Replace Only the First Occurrence of a Character in a Java String

There might be more than one occurrence of the same character we want to replace in a string. If we want to replace only the character’s first occurrence and ignore other occurrences after that. It can be done using another method of the String class, which is replaceFirst(). As its name suggests, it replaces only the first character of a string.

In the example, we have a string with two &, and we only want to replace the first one with a coma as we did in the previous example, but ignore the second &. So, we use oldString.replaceFirst(oldChar, newChar) to pass whitespace with & and a coma. The output shows the final result.

public class ReplaceCharString {
    public static void main(String[] args) {

        String oldString1 = "I have used multiple Internet providers & but my current provider is AT&T.";

        String newString1 = oldString1.replaceFirst(" &", ",");

        System.out.println(newString1);

    }
}

Output:

I have used multiple Internet providerss, but my current provider is AT&T.

String.replace() to Replace Two Characters in a String in Java

In the last example of this tutorial, we will use replace() to replace two different characters. In oldString1, we want to replace the capital letter character (V) with a small letter character (v), and the last character of the string, coma , with ..

We can do this in a single line by joining two replace() methods and then passing the proper characters.

public class ReplaceCharString {
    public static void main(String[] args) {

        String oldString1 = "My name is Sam and I am a Software DeVeloper,";

        String newString1 = oldString1.replace("V", "v").replace(",", ".");

        System.out.println(newString1);

    }
}

Output:

My name is Sam and I am a Software Developer.

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