扫描仪NoSuchElementException [英] Scanner NoSuchElementException
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;
}
}
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;
}
}
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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