String.length() / charAt()

// Returns the number of characters in the string.
string.length();

// Returns the character at the specified position (0-based index).
string.charAt(int index);

// Returns the Unicode code point at the specified position.
string.codePointAt(int index);

// Get the length of a string.
String str = "Hello";
System.out.println(str.length()); // Outputs: 5

// Get the length of a Japanese string.
String name = "山田太郎";
System.out.println(name.length()); // Outputs: 4

// Get the character at a specific position.
String word = "Java";
char c = word.charAt(0);
System.out.println(c); // Outputs: J

// Loop through a string one character at a time.
String text = "abc";
for (int i = 0; i < text.length(); i++) {
    System.out.println(text.charAt(i)); // Outputs: a, b, c in order
}

// Get the code point of a character.
String emoji = "😊abc";
System.out.println(emoji.codePointAt(0)); // Outputs the emoji's code point: 128522

length() is one of the most commonly used string methods in Java and returns the number of characters in a string. Passing a negative index or an index greater than or equal to the string length throws a StringIndexOutOfBoundsException, so always check the range beforehand.

charAt() returns the character at the specified position as a char type. Because char represents a single UTF-16 code unit, use codePointAt() to correctly handle surrogate pair characters such as emoji.

To extract a portion of a string, use substring(). To search within a string, use indexOf() / contains().