How can I check if a single character appears in a string?

To check if a single character appears in a string in Java, you can use the indexOf method of the String class.

Here's an example of how you can use the indexOf method to check if a character appears in a string:

String s = "Hello, world!";
char c = 'o';

if (s.indexOf(c) >= 0) {
  // character appears in string
} else {
  // character does not appear in string
}

The indexOf method returns the index of the first occurrence of the character in the string, or -1 if the character does not appear in the string.

Alternatively, you can use the contains method of the String class to check if a character appears in a string:

String s = "Hello, world!";
char c = 'o';

if (s.contains(String.valueOf(c))) {
  // character appears in string
} else {
  // character does not appear in string
}

This will also check if the character appears in the string.

Note that the indexOf and contains methods are