被塞在“线程”主体中的异常“ java.util.NoSuchElementException [英] Stuck at "Exception in thread "main" java.util.NoSuchElementException

问题描述

我写了一个程序与一个单独的类，但我不断得到相同的错误，在用户输入三面之后。

主要代码是：

  package interactiveTriangleWithAClass; 
 
 public class InteractiveTriangleProgramClass 
 
 {public static void main（String [] args）throws Exception 
 {IAclass nums = new IAclass（）; 
双周长; 
双面积; 
 
 explain（）; 
 
 nums.getNumbers（）; 
 
 circles = nums.calcPer（）; 
 
 area = nums.calcArea（）; 
 
 outputResults（nums，peripheral，area）; } 
 
 public static void explain（）
 
 {System.out.println（此程序计算周长）; 
 System.out.print（和三角形三角形的面积）; 
 System.out.println（3个数字由用户输入。\\
 +输出是3个数字，周长和面积。\
 +使用单独的课程。\\
 +Derek Michel编写的程序）; } 
 
 public static void outputResults（IAclass nums，double area，double boundaries）throws Exception 
 
 {nums.getNumbers（）; 
 System.out.println（）; 
 System.out.println（周长是+周界）; 
 System.out.print（和区域是+区域）; 
} 
  

课程是：

  package interactiveTriangleWithAClass; 
 import java.util。*; 
 public class IAclass {
 private double num1，num2，num3; 
 public IAclass（）{
 num1 = num2 = num3 = 3; 
} 
 public IAclass（double value1，double value2，double value3）{
 num1 = value1; 
 num2 = value2; 
 num3 = value3; 
} 
 public void getNumbers（）throws异常{
扫描仪控制台=新的扫描仪（System。in）; 
 System.out.println（Enter the first side。）; 
 num1 = console.nextDouble（）; 
 System.out.println（进入第二边）; 
 num2 = console.nextDouble（）; 
 System.out.println（进入第三边）; 
 num3 = console.nextDouble（）; 
 console.close（）; 
 while（num1 <= 0）{
 System.err.print（Error。Side one must be greater than 0.）; 
 System.out.println（再次输入一个。）; 
 num1 = console.nextDouble（）; 
} 
 while（num2 <= 0）{
 System.err.print（Error。Side two must be than than 0.）; 
 System.out.println（再次输入二号）; 
 num2 = console.nextDouble（）; 
} 
 while（num3 <= 0）{
 System.err.print（Error。Side three must be greater than 0.）; 
 System.out.println（再次输入三号）; 
 num3 = console.nextDouble（）; 
} 
 if（num1 + num2< num3）{
 System.out.println（基于输入的三角形）; 
 System.out.print（不可能创建）; 
 System.exit（0）; 
} 
 if（num2 + num3< num1）{
 System.out.println（基于输入的三角形）; 
 System.out.print（不可能创建）; 
 System.exit（0）; 
} 
 if（num1 + num3< num2）{
 System.out.println（基于输入的三角形）; 
 System.out.print（不可能创建）; 
 System.exit（0）; 
} 
} 
 public double calcPer（）{
 return（num1 + num2 + num3）; 
} 
 public double calcArea（）{
 double s; 
 s =（num1 + num2 + num3）/ 2; 
 return（Math.sqrt（s *（s  -  num1）*（s  -  num2）*（s  -  num3）））; 
} 
 public void outputNumbers（）{
 System.out.print（两边是+ num1 +，+ num2）; 
 System.out.print（and+ num3）; 
} 
} 
  

控制台运行后读取此内容，输入：

 线程main中的异常java.util.NoSuchElementException 
在java.util.Scanner.throwFor（未知源）
在java.util.Scanner.next（未知源）
在java.util.Scanner.nextDouble（未知源）
在interactiveTriangleWithAClass.IAclass.getNumbers（IAclass.java： 48）
在interactiveTriangleWithAClass.InteractiveTriangleProgramClass.outputResults（InteractiveTriangleProgramClass.java:54）
在interactiveTriangleWithAClass.InteractiveTriangleProgramClass.main（InteractiveTriangleProgramClass.java:41）
  

解决方案

尝试删除以下行：

 code> console.close（）; 
  

您无法从控制台中读取你已经关闭了它。

你几乎肯定不应该明确地关闭你的 Scanner ：这样做会关闭 System.in 。关闭您尚未打开自己的流并不是一个好习惯，因为一些其他代码可能依赖流被打开，并且在不存在的情况下抛出异常。

调试这样一个问题 - 异常可能会因为这个原因潜在地被抛出来 - 是非常棘手的。

I wrote a program with a separate class but I keep getting the same error right after the user inputs the three sides.

The main code is:

package interactiveTriangleWithAClass;

public class InteractiveTriangleProgramClass

{ public static void main (String [] args) throws Exception
  { IAclass nums = new IAclass();
    double perimeter;
    double area;

    explain();

    nums.getNumbers();

    perimeter = nums.calcPer();

    area = nums.calcArea();

    outputResults(nums, perimeter, area);   }

  public static void explain()

  { System.out.println("This program calculates the perimeter ");
    System.out.print("and the area of 3 sides for a triangle. ");
    System.out.println("The 3 numbers are entered by the user.\n"
      + "The output is the 3 numbers, the perimeter and the area.\n"
      + "A seperate class is used.\n"
      + "Program written by Derek Michel");  }

  public static void outputResults(IAclass nums, double area, double perimeter) throws Exception

  { nums.getNumbers();
    System.out.println();
    System.out.println("The perimeter is " + perimeter);
    System.out.print(" and the area is " + area); } 
}

The class is:

package interactiveTriangleWithAClass;
import java.util.*;
public class IAclass {
    private double num1, num2, num3;
    public IAclass() {
        num1 = num2 = num3 = 3;
    }
    public IAclass(double value1, double value2, double value3) {
        num1 = value1;
        num2 = value2;
        num3 = value3;
    }
    public void getNumbers() throws Exception {
        Scanner console = new Scanner(System. in );
        System.out.println("Enter the first side.");
        num1 = console.nextDouble();
        System.out.println("Enter the second side.");
        num2 = console.nextDouble();
        System.out.println("Enter the third side.");
        num3 = console.nextDouble();
        console.close();
        while (num1 <= 0) {
            System.err.print("Error. Side one must be greater than 0.");
            System.out.println("Enter side one again.");
            num1 = console.nextDouble();
        }
        while (num2 <= 0) {
            System.err.print("Error. Side two must be greater than 0.");
            System.out.println("Enter side two again.");
            num2 = console.nextDouble();
        }
        while (num3 <= 0) {
            System.err.print("Error. Side three must be greater than 0.");
            System.out.println("Enter side three again.");
            num3 = console.nextDouble();
        }
        if (num1 + num2 < num3) {
            System.out.println("Based on the sides inputed, your triangle ");
            System.out.print("is impossible to create.");
            System.exit(0);
        }
        if (num2 + num3 < num1) {
            System.out.println("Based on the sides inputed, your triangle ");
            System.out.print("is impossible to create.");
            System.exit(0);
        }
        if (num1 + num3 < num2) {
            System.out.println("Based on the sides inputed, your triangle ");
            System.out.print("is impossible to create.");
            System.exit(0);
        }
    }
    public double calcPer() {
        return (num1 + num2 + num3);
    }
    public double calcArea() {
        double s;
        s = (num1 + num2 + num3) / 2;
        return (Math.sqrt(s * (s - num1) * (s - num2) * (s - num3)));
    }
    public void outputNumbers() {
        System.out.print("The sides are " + num1 + ", " + num2);
        System.out.print(" and" + num3);
    }
}

The console reads this after running and after 3 sides are inputed:

Exception in thread "main" java.util.NoSuchElementException
    at java.util.Scanner.throwFor(Unknown Source)
    at java.util.Scanner.next(Unknown Source)
    at java.util.Scanner.nextDouble(Unknown Source)
    at interactiveTriangleWithAClass.IAclass.getNumbers(IAclass.java:48)
    at interactiveTriangleWithAClass.InteractiveTriangleProgramClass.outputResults(InteractiveTriangleProgramClass.java:54)
    at interactiveTriangleWithAClass.InteractiveTriangleProgramClass.main(InteractiveTriangleProgramClass.java:41)

解决方案

Try removing the following line:

console.close();

You can't read from console once you've closed it.

You almost certainly shouldn't explicitly close your Scanner: doing so will close System.in. It is not a good practice to close a stream that you haven't opened yourself, since some other code may rely on the stream being open, and throw an exception when it isn't.

Debugging such a problem - where the exception is potentially thrown a long way from the cause - is very tricky.

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