how to uppercase the first letter of a string in java

String str = "java";
String cap = str.substring(0, 1).toUpperCase() + str.substring(1);
// cap = "Java"

StringUtils.capitalize(..)

String str = "java";
str = str.substring(0, 1).toUpperCase() + str.substring(1);
// str = "Java"

String str = "hello world!";

// capitalize first letter
String output = str.substring(0, 1).toUpperCase() + str.substring(1);

// print the string
System.out.println(output);
// Hello world!

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

    // create a string
    String message = "everyone loves java";

    // stores each characters to a char array
    char[] charArray = message.toCharArray();
    boolean foundSpace = true;

    for(int i = 0; i < charArray.length; i++) {

      // if the array element is a letter
      if(Character.isLetter(charArray[i])) {

        // check space is present before the letter
        if(foundSpace) {

          // change the letter into uppercase
          charArray[i] = Character.toUpperCase(charArray[i]);
          foundSpace = false;
        }
      }

      else {
        // if the new character is not character
        foundSpace = true;
      }
    }

    // convert the char array to the string
    message = String.valueOf(charArray);
    System.out.println("Message: " + message);
  }
}

String str = "java";
String cap = str.substring(0, 1).toUpperCase() + str.substring(1);
// cap = "Java"