พื้นฐานเจเนอิกส์ (T และการอนุมานชนิด)

public class Main {
  // A tiny generic container
  static class Box<T> {
    private T value;
    void set(T v) { value = v; }
    T get() { return value; }
  }

  public static void main(String[] args) {
    Box<String> bs = new Box<String>(); // T becomes String
    bs.set("hello");
    System.out.println(bs.get());       // no cast needed

    // Box<Integer> bi = new Box<Integer>();
    // bi.set("oops"); // would not compile: String is not Integer
  }
}

public class Main {
  static class Box<T> {
    private T value;
    Box() {}
    Box(T v) { value = v; }
    T get() { return value; }
  }

  public static void main(String[] args) {
    // Type on the left, diamond on the right — compiler infers T
    Box<Integer> a = new Box<>(123);
    Box<String> b = new Box<>("hi");

    System.out.println(a.get() + 1);    // 124
    System.out.println(b.get().toUpperCase());
  }
}

public class Main {
  // Generic method: works for any Comparable type
  static <T extends Comparable<T>> T min(T a, T b) {
    return (a.compareTo(b) <= 0) ? a : b;
  }

  public static void main(String[] args) {
    System.out.println(min(3, 7));              // Integer
    System.out.println(min("apple", "banana")); // String (lexicographic)
  }
}