Question

我在尝试运行代码时遇到错误

Project1.java:5：不兼容的类型发现：无效必需：java.lang.String String creditcard = mainintro（）; ^ Project1.java:14：无法从结果类型为void的方法返回值返回信用卡; ^ 2个错误

import java.util.*; // so that I can use Scanner

public class Project1{
public static void main(String[] arg){
    String creditcard=mainintro();
    checksize(creditcard);
    checkprefix(creditcard);
}

public static void mainintro(){//Displays the intro message
    Scanner console = new Scanner(System.in);
    System.out.println("Enter a credit card number from 13 to 16 digits      long:");
    String creditcard = console.next();
    return creditcard;
}

public static void checksize(String size){

int stringsize=size.length();//The Length of the creditcard

if(stringsize>=17||stringsize<=12){//Checks the size
System.out.println("The Credit card must be 13 to 16 numbers.");
System.out.println("");
System.out.println(size);
mainintro();
}else{System.out.println(size);}

}

public static void checkprefix(String creditcard){
System.out.println(creditcard);
}
}

如果我定义String creditcard =“”;在主要它工作，但只使用“”作为变量？我该如何解决这个问题？

Answer 1

变化：

public static void mainintro()

要：

public static String mainintro()

具有字符串void java的返回值的不兼容类型

1 个答案: