Learning to use methods, keep getting error: "cannot convert from void to int"

Question

我正在尝试制作一个脚本，使用方法打印出最大和最小的数字，但是我不知道为什么我的方法不起作用......我在我不断得到的地方旁边发表了评论错误。

我真的不需要帮助让脚本工作，但是如果有人能向我解释为什么我的方法不起作用，我将不胜感激。

代码如下：

import java.util.Scanner;

public class MinMax {
    public static void main(String[] args) {
        int nr1, nr2, nr3, biggest, smallest;
        Scanner lukija = new Scanner(System.in);

        System.out.print("Input first value: ");
        nr1 = lukija.nextInt();

        System.out.print("Input second value: ");
        nr2 = lukija.nextInt();

        System.out.print("Input third value: ");
        nr3 = lukija.nextInt();

        biggest = biggest(nr1, nr2, nr3); // here is where I keep getting the error
        smallest = smallest(nr1, nr2, nr3); // here too

        System.out.print(biggest + " was the biggest number.");
        System.out.print(smallest + " was the smallest number.");

    }


public static void biggest(int nr1, int nr2, int nr3){

    int biggest = 0;

    if (nr1>nr2 && nr1>nr3){
        nr1=biggest;
    } else if (nr2>nr1 && nr2>nr3){
        nr2=biggest;
    } else if (nr3>nr1 && nr3>nr2){
        nr3=biggest;
    }


}

public static void smallest(int nr1, int nr2, int nr3){

    int smallest = 0;

    if (nr1<nr2 && nr1<nr3){
        nr1=smallest;
    } else if (nr2<nr1 && nr2<nr3){
        nr2=smallest;
    } else if (nr3<nr1 && nr3<nr2){
        nr3=smallest;
    }


}
}

Answer 1

修改方法的 return 签名，将值赋给 smallest（或 biggest），然后 return 变量。喜欢，

public static int biggest(int nr1, int nr2, int nr3){
    int biggest = 0;

    if (nr1>nr2 && nr1>nr3){
        biggest = nr1;
    } else if (nr2>nr1 && nr2>nr3){
        biggest = nr2;
    } else if (nr3>nr1 && nr3>nr2){
        biggest = nr3;
    }
    return biggest;
}

public static int smallest(int nr1, int nr2, int nr3){
    int smallest = 0;
    if (nr1<nr2 && nr1<nr3){
        smallest = nr1;
    } else if (nr2<nr1 && nr2<nr3){
        smallest = nr2;
    } else if (nr3<nr1 && nr3<nr2){
        // nr3=smallest;
        smallest = nr3;
    }
    return smallest;
}

你可以像这样简化上面的内容

public static int biggest(int nr1, int nr2, int nr3){
    int biggest = Math.max(nr1, nr2);
    return Math.max(biggest, nr3);
}

public static int smallest(int nr1, int nr2, int nr3){
    int smallest = Math.min(nr1, nr2);
    return Math.min(smallest, nr3);
}

Answer 2

问题是您试图从一个没有 return 任何东西的方法中为变量赋值。

biggest = biggest(nr1, nr2, nr3); // here is where I keep getting the error

请注意，您的方法签名设置为 void，这意味着不会 returned

public static void biggest(int nr1, int nr2, int nr3) {}

您的 biggest() 和 smallest() 方法应该 return biggest/smallest 值，方法签名中的 void 应该 int.