要设置限制（1或2）时需要一个随机数？

Question

I am attempting to create a method where a user predicts if a simulated coin toss will be heads or tails. I am having trouble getting the random number to assign to just 1 or 2 (for heads of tails). I believe my attempt(code below) is giving me 0, 1 and 2.

public static void coinToss(String call){
        //setting up random
        Random random = new Random();

        //set user guess to numeric value
        int guessNo=0;


        if (call.equalsIgnoreCase("heads")){
            guessNo=1;
        }else if (call.equalsIgnoreCase("tails")){
            guessNo=2;
        }else System.out.println("Invalid. Enter either heads or tails");

        //setting result for coin toss 
        **int result = random.nextInt(2);**
        System.out.println("Trace: numberic result is:" + result);

        //if...else statement to print results of coin toss
        if (result==1){
            System.out.println("Result: heads");
        }else if (result==2){
            System.out.println("Result: Tails");
        }else System.out.println("Invalid result");

        if (guessNo==result){
            System.out.println("Guess Correct");
        }else System.out.println("Guess incorrect");

    }//method end

I am a relative java newbie (obviously!) so Many thanks in advance for any help!

Answer 1

The answers suggesting adding one to the nextInt(2) result are correct, but may not be the right long term strategy. In many ways, Java prefers sequences of numbers to start, whenever possible, at 0. For example, array index values run from 0 through length-1.

It may be better to change your internal encoding of the heads/tails to use [0,1] rather than [1,2], and use the nextInt result directly.

Answer 2

int result = (random.nextInt(2))+1; is what you might want to try.

Answer 3

As documented, Random::nextInt supplies a random number between 0 (inclusive) and the specified upper limit (exclusive). You must therefore first obtain a random number from the range [0,2> and then add 1 to that.