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Magic 8 ball

Java Syntax, Level 9, Lesson 2

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I've written some code that seems logical to me. Why is it still not meeting the requirements I wonder?

In this task, you need to implement a getPrediction() method in the MagicBall class that works like a magic 8 ball.
It returns a randomly chosen response to a question. In the getPrediction() method, you need to use the Random class's nextInt(int) method, which should return values from 0 to 7 inclusive.
Depending on the value returned by nextInt(int), it returns one of these possible responses:
0 -> Certainly
1 -> Definitely
2 -> Most likely
3 -> The outlook is good
4 -> Ask later
5 -> Try again
6 -> My answer is no
7 -> Very doubtful
Otherwise return null.

Requirements:

Implement the getPrediction() method in accordance with the task conditions.

package en.codegym.task.pro.task08.task0805; /* Magic 8 ball */ public class Solution { public static void main(String[] args) { System.out.println("Will I make enough money to buy a BMW?"); System.out.println(MagicBall.getPrediction()); } }

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Guadalupe Gagnon

Level 37 , Tampa, United States

3 April, 13:15

You need break; after each case statement:

case 1:
   // do something
   break;
case 2:
   // do something
   break;
//etc..

Guadalupe Gagnon

Level 37 , Tampa, United States

4 April, 17:08

This is because switch statements will jump to the case that is true and then execute all the code following until a break statement is reached, even code under other cases. Take this code as an example:

public static void main(String[] args) {
   int temp[] = {0, 4, 6};

   for(int x : temp) {
      System.out.println("Testing: " + x);
      switch (x) {
         case 0:
            System.out.println(0);
         case 1:
            System.out.println(1);
         case 2:
            System.out.println(2);
         case 3:
            System.out.println(3);
         case 4:
            System.out.println(4);
         case 5:
            System.out.println(5);
         case 6:
            System.out.println(6);
         case 7:
            System.out.println(7);
      }
      System.out.println();
   }
}

In it it takes 3 numbers in an array and tests them with the switch statement. The results if you ran it would be as follows: - The number 0 will jump to case 0 and then output every single line of code that follows, which is every line in the switch statement - The number 4 will jump to case 4 and then output the rest of the lines that follow, which are 4-7 - The number 6 will jump to case 6 and then output the rest of the lines that follow, which are 6 and 7 In this example the case statements are in numerical order, but I could shuffle those up and it would still behave as I stated above: jumping to the case statement that is true and then outputting all the code that follows until a break is reached.

Evgeniia Shabaeva

Level 11 , Budapest, Hungary

9 April, 06:35

Thank you very much!

Thomas

Level 41 , Bayreuth, Germany

9 April, 10:41

Unfortunately CG is still on Java 8 (or 13 for the new pro tasks, I don't know for sure). From 14 on you could use the new switch-case. That has several advantages. 1. It has a return value. Means you don not need to use a variable and assign values to it or return values from inside each case statement. 2. It has no fallthrough. 3. and related to no fallthrough is, that you now can group cases

case 1: ...
case 2: ...
case 3: ...
             break;

// now simpley is written
case 1, 2, 3 -> ...

The getPrediction() method would look like:

public static String getPrediction() {
    return switch(new Random().nextInt(0, 8)) {
        case 0 -> CERTAIN;
        case 1 -> DEFINITELY;
        case 2 -> MOST_LIKELY;
        case 3 -> OUTLOOK_GOOD;
        case 4 -> ASK_AGAIN_LATER;
        case 5 -> TRY_AGAIN;
        case 6 -> NO;
        case 7 -> VERY_DOUBTFUL;
        default -> throw new IllegalStateException("Unexpected value");
    };
}