Boxing and Unboxing

  • Boxing in Java refers to the process of converting a primitive data type into its corresponding wrapper class (e.g., int to Integerdouble to Double, etc.).
  • Unboxing is the reverse process, converting a wrapper class object back into its corresponding primitive data type (e.g., Integer to intDouble to double, etc.)
// boxing
List<Integer> li = new ArrayList<>();
for (int i = 1; i < 50; i += 2)
// unboxing
public static int sumEven(List<Integer> li) {
    int sum = 0;
    for (Integer i: li)
        if (i % 2 == 0)
            sum += i;
	return sum;