扫描仪NoSuchElementException [英] Scanner NoSuchElementException
本文介绍了扫描仪NoSuchElementException的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
java.util.NoSuchElementException：找不到行
我正在使用 Scanner（System.in），程序不断读取任何内容，重复无效格式例外文字。如果我输入正确的价值 int ，第一部分通过，然后 double 部分立即进入此异常。如果我输入一个不正确的价值 int ，那么它开始循环异常。
这是我的代码：
import java.util.Scanner ;
public class Program_4 {
public static void main（String [] args）{
getValidInt（输入从5到50的整数，5,50 ）;
getValidDouble（从5.0到50.0输入一个double，5.0,50.0）;
getValidString（输入长度为5到8个字符的字符串，5,8）;
}
public static int getInt（String prompt）
{
扫描仪sc = new Scanner（System.in）;
int i = 0;
boolean isValid;
do
{
try
{
System.out.print（prompt +：）;
i = Integer.parseInt（sc.nextLine（））;
isValid = true;
}
catch（异常e）
{
System.out.println（e）;
System.out.print（Invalid Format：）;
isValid = false;
}
}
while（isValid == false）;
sc.close（）;
return i;
}
public static int getValidInt（String prompt，int min，int max）
{
int i = 0;
boolean isValid = false;
do
{
i = getInt（prompt）;
if（i< min）System.out.println（Value must be> =+ min）;
else if（i> max）System.out.println（Value must be <=+ max）;
else isValid = true;
} while（isValid == false）;
return i;
}
public static double getDouble（String prompt）
{
扫描仪sc = new Scanner（System.in）;
double i = 0.0;
boolean isValid;
do
{
try
{
System.out.print（prompt +：）;
i = Double.parseDouble（sc.nextLine（））;
isValid = true;
}
catch（异常e）
{
System.out.println（e）;
System.out.println（Invalid Format：）;
isValid = false;
}
} while（isValid == false）;
sc.close（）;
return i;
}
public static double getValidDouble（String prompt，double min，double max）
{
int i = 0;
boolean isValid = false;
do
{
i = getInt（prompt）;
if（i< min）System.out.println（Value must be> =+ min）;
else if（i> max）System.out.println（Value must be <=+ max）;
else isValid = true;
} while（isValid == false）;
return i;
}
public static String getString（String prompt）
{
扫描仪sc = new Scanner（System.in）;
String i =;
boolean isValid;
do
{
try
{
System.out.print（prompt +：）;
i = sc.nextLine（）;
isValid = true;
}
catch（异常e）
{
System.out.print（Invalid Format：）;
isValid = false;
}
} while（isValid == false）;
sc.close（）;
return i;
}
public static String getValidString（String prompt，int min，int max）
{
String i;
boolean isValid = false;
do
{
i = getString（prompt）;
if（i.length（）< min）System.out.println（String必须大于+ min +个字符。
else if（i.length（）> max）System.out.println（String必须大于+ max +个字符。
else isValid = true;
} while（isValid == false）;
return i;
}
}
解决方案
你有多个 Scanner ，您关闭，它关闭底层的 InputStream ，因此另一个扫描器不能再从相同的 InputStream 和 NoSuchElementException 结果中读取。
对于控制台应用程序，使用单个 Scanner 从 System.in 。
I'm having a problem with my Java assignment. I'm getting an unexpected exception, specifically:
java.util.NoSuchElementException: No line found
I am using Scanner(System.in) and the program is continually reading nothing and repeating the "invalid format" exception text. If I enter a correctly valued int, the first part passes and then the double part immediately goes into this exception. If I enter an incorrectly valued int, then it starts looping the exception.
Here is my code:
import java.util.Scanner;
public class Program_4 {
public static void main(String[] args) {
getValidInt("Enter an integer from 5 to 50",5,50);
getValidDouble("Enter a double from 5.0 to 50.0",5.0,50.0);
getValidString("Enter a string with length from 5 to 8 characters",5,8);
}
public static int getInt(String prompt)
{
Scanner sc = new Scanner(System.in);
int i = 0;
boolean isValid;
do
{
try
{
System.out.print(prompt + ": ");
i = Integer.parseInt(sc.nextLine());
isValid = true;
}
catch (Exception e)
{
System.out.println(e);
System.out.print("Invalid Format: ");
isValid = false;
}
}
while (isValid == false);
sc.close();
return i;
}
public static int getValidInt(String prompt, int min, int max)
{
int i = 0;
boolean isValid = false;
do
{
i = getInt(prompt);
if(i < min) System.out.println("Value must be >= " + min);
else if(i > max) System.out.println("Value must be <= " + max);
else isValid = true;
} while (isValid == false);
return i;
}
public static double getDouble(String prompt)
{
Scanner sc = new Scanner(System.in);
double i = 0.0;
boolean isValid;
do
{
try
{
System.out.print(prompt + ": ");
i = Double.parseDouble(sc.nextLine());
isValid = true;
}
catch (Exception e)
{
System.out.println(e);
System.out.println("Invalid Format: ");
isValid = false;
}
} while (isValid == false);
sc.close();
return i;
}
public static double getValidDouble(String prompt, double min, double max)
{
int i = 0;
boolean isValid = false;
do
{
i = getInt(prompt);
if(i < min) System.out.println("Value must be >= " + min);
else if(i > max) System.out.println("Value must be <= " + max);
else isValid = true;
} while (isValid == false);
return i;
}
public static String getString(String prompt)
{
Scanner sc = new Scanner(System.in);
String i="";
boolean isValid;
do
{
try
{
System.out.print(prompt + ": ");
i = sc.nextLine();
isValid = true;
}
catch (Exception e)
{
System.out.print("Invalid Format: ");
isValid = false;
}
} while (isValid == false);
sc.close();
return i;
}
public static String getValidString(String prompt, int min, int max)
{
String i;
boolean isValid = false;
do
{
i = getString(prompt);
if(i.length() < min) System.out.println("String must be more than " + min + " characters.");
else if(i.length() > max) System.out.println("String must be more than " + max + " characters.");
else isValid = true;
} while (isValid == false);
return i;
}
}
解决方案
You have more than one Scanner that you close, which closes the underlying InputStream, therefore another Scanner can no longer read from the same InputStream and a NoSuchElementException results.
For console apps, use a single Scanner to read from System.in.
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