扫描仪作为参数并转换为int？（爪哇）

Question

我在使用扫描仪方面遇到了问题。getUserInput将scanner实例作为输入，并初始化来自scanner的指定大小的数组。例如：如果用户输入3，那么该方法将创建一个大小为3的数组。

然而，它一直说scnr不能转换为int......有什么建议吗？

 public static void main(String[] args) 
  {
  Scanner scnr = new Scanner(System.in);
  System.out.println("How many orders were placed Saturday?");
  int [] userInput = getUserInput(scnr);
  System.out.println("How many orders were placed Sunday?");
  int [] userInput = getUserInput(scnr);
  System.out.println("How many orders were placed Monday?");
  int [] userInput = getUserInput(scnr) 

  return;
 }
}


 public static int[] getUserInput(Scanner scnr)
 {
   int[] userInput = new int[scnr];

   return userInput;   
 }

Answer 1

首先，你在这里犯了两个错误

1. int[]userInput此userInput变量有两个重复项
2. 您正在将Scanner的一个实例作为参数传递给getUserInput函数

修复

所以为了创造，我们需要遵循一个语法，即

datatype [] vairable_name = new datatype[size]; 

这里的大小可以是byteshortint，但您所做的是

datatype [] vairable_name = new datatype[Scanner];

这不是语法。您可以通过从用户处获取int输入来修复它
一个扫描器作为一种方法。nextInt（），它将用户输入的数字转换为int<解决方法是

int[] userInput = new int[scnr.nextInt()];
// This is like the syntax 
datatype [] vairable_name = new datatype[Scanner];

重复变量

你应该修改java中的作用域，然后你就会知道为什么这是一个错误
同一作用域或子作用域中不能有相同的变量名

public static void main(String args[]){
   int a = 0;
   int a = 1; // <- error cuz a is already difined and is duplicate in the same scope.
}

同样地

public static void main(String args[]){
   int a = 0;
   if(true){
      int a = 1; // <- error cuz a is already difined and is duplicate in child scope.
   }
}

解决方案是更改变量名。

//scnr is now globally available in the class so need to pass it as a parameter 
Scanner scnr = new Scanner(System.in);
public static void main(String[] args) 
  {
  System.out.println("How many orders were placed Saturday?");
  int [] saturdayUserInput = getUserInput();
  System.out.println("How many orders were placed Sunday?");
  int [] sundayUserInput = getUserInput();
  System.out.println("How many orders were placed Monday?");
  int [] mondayUserInput = getUserInput() 

  return;
 }
}

 public static int[] getUserInput()
 {
   int[] userInput = new int[scnr.nextInt()];

   return userInput;   
 }

Answer 2

Java Scanner类的nextInt（）方法用于将输入的下一个标记扫描为int

public static int[] getUserInput(Scanner scnr)
     {
       int[] userInput = new int[scnr.nextInt()];
    
       return userInput;   
     }

Answer 3

你必须在Scanner上调用一个方法。因为你想要一个int，所以这样做：

int[] userInput = new int[scnr.nextInt()];

在这里您可以找到API文档：https://docs.oracle.com/javase/8/docs/api/java/util/Scanner.html