Opérations sur chaînes et StringBuilder

public class StringDemo {
    public static void main(String[] args) {
        String s = "Hello, World";

        System.out.println(s.length());
        System.out.println(s.substring(0, 5));   // Hello
        System.out.println(s.charAt(7));         // W

        String[] parts = s.split(", ");
        String joined = String.join(" | ", parts);

        boolean has = s.contains("World");
        int idx = s.indexOf("o");

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 3; i++) sb.append(i);
        System.out.println(sb); // 012

        String json = """
            {"name": "Alice"}
            """;
        System.out.println(json);
    }
}