1 · Values and control flow · 25 MIN

Types, methods and conditions

A method turns a declared input type into a declared result type.

Java checks types before running a program. A static method can be called without creating an instance and makes a useful starting point for pure calculations. The conditional here includes the boundary score of 60. String is a reference type; use equals for content comparison rather than ==. Keep your output separate from decisions so tests can call the decision method directly. Primitive int is fixed-width and overflow is not automatically reported by ordinary arithmetic.

Write down the interval for each grade before writing branches.

Read the example

public class Main {
  static String result(int score) { return score >= 60 ? "Pass" : "Try again"; }
  public static void main(String[] args) {
    System.out.println(result(60));
    System.out.println(result(59));
  }
}

Pass
Try again

Your challenge

Add a grade method that returns A for at least 90, B for at least 75 and C otherwise; reject scores outside 0–100.

Solution cost: O(1) comparisons. time · O(1) auxiliary state. space

Common trap

Order overlapping conditions from most specific to least specific.

public class Main {
  static String result(int score) { return score >= 60 ? "Pass" : "Try again"; }
  public static void main(String[] args) {
    System.out.println(result(60));
    System.out.println(result(59));
  }
}

Further reading: Official documentation