Generic methods

Definition

A generic method has its own type parameter, written before the return type. Java works out the type from the arguments, so one method can serve many types safely.

Example code

One method that works for any list or array

import java.util.List;

class Util {
    static <T> T firstOf(List<T> list) {
        return list.get(0);
    }

    static <T> void swap(T[] array, int i, int j) {
        T temp = array[i];
        array[i] = array[j];
        array[j] = temp;
    }
}

class Demo {
    public static void main(String[] args) {
        String firstName = Util.firstOf(List.of("Asha", "Ravi"));   // T is String
        int firstNumber = Util.firstOf(List.of(10, 20, 30));        // T is Integer
        System.out.println(firstName + " " + firstNumber);

        Integer[] numbers = {1, 2, 3};
        Util.swap(numbers, 0, 2);
        System.out.println(java.util.Arrays.toString(numbers));
    }
}

// Output:
// Asha 10
// [3, 2, 1]