Summary - Method parameters

Combine primitive, object and varargs to write a statistics function.

Summary: Method parameters

In this group you saw four aspects of parameter passing: primitive pass by value, object references, varargs and final parameters.

Primitive parameters are copied; the outside is not affected. Object parameters pass a copy of the reference; content changes affect the outside. With varargs you can accept a flexible number of arguments. final prevents reassignment.

Now you will combine these to write a small statistics function: take numbers via varargs and return min and max as an array.

Exercise Statistics function

Define a static int[] method called minMax; parameter int... nums. The body should scan all elements to find the smallest and the largest; return new int[]{min, max}. In main, call minMax(4, 9, 2, 7) and print the result with Arrays.toString.

Show example solution

static int[] minMax(int... nums) {
  int min = Integer.MAX_VALUE;
  int max = Integer.MIN_VALUE;
  for (int n : nums) {
    if (n < min) min = n;
    if (n > max) max = n;
  }
  return new int[]{min, max};
}
// inside main:
System.out.println(Arrays.toString(minMax(4, 9, 2, 7)));

Test yourself

Fill in the blank: varargs declaration

static int[] minMax(int____ nums) {
  int min = Integer.MAX_VALUE;
  int max = Integer.MIN_VALUE;
  for (int n : nums) {
    if (n < min) min = n;
    if (n > max) max = n;
  }
  return new int[]{min, max};
}

Show answer

static int[] minMax(int... nums) {
  int min = Integer.MAX_VALUE;
  int max = Integer.MIN_VALUE;
  for (int n : nums) {
    if (n < min) min = n;
    if (n > max) max = n;
  }
  return new int[]{min, max};
}

Match scenario to approach

Flexible count of numbers

varargs
Change the outer list

object parameter
Prevent reassignment

final parameter
Keep the primitive value safe

pass by value
Which call is valid for a method with int... nums parameter?
- sum(1, 2, 3)
- sum{1, 2, 3}
- sum([1, 2, 3])
- sum(int 1, 2, 3)
Show answer

sum([1, 2, 3]) — A varargs call takes comma-separated arguments.

Next lesson: Task model

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