我的代码中出现 NameFormatException 并且跳过了代码的特定部分？

Question

我已经编写了一个程序来接受两个学生的数据，但是当我运行这段代码时， 'name' 部分第二次被跳过并且它从主题开始并给出 NameformatException？第一个运行代码是正常的，但是当它进入第二个运行时，名称部分被跳过，我必须直接输入整数值，如果我不输入，我会得到 NumberFormatException。

import java.util.Scanner;

    @SuppressWarnings("serial")
    class NegativeValueException extends Exception {
        
        public  NegativeValueException() {
            
        
    }
        }
    @SuppressWarnings("serial")
    class ValueOutOfRange extends Exception{
        public ValueOutOfRange() {
            System.out.println("Value out of range Exception");
        }
    }
public class Student1 {
    
    public static void main(String[] args) {
        
        Scanner sc = new Scanner(System.in);
        for(int i=0;i<2;i++) {
            String[] name = new String[2];
            int sub1=0;
            int sub2=0;
            int sub3=0;
            double avg;

            
            
            try {
            
                System.out.println("Enter the data of Student "+(i+1)+" : ");
                
                
                name[i] = sc.nextLine();
                if(name[i].equals(null))
                    break;
                else
                if(sc.hasNextInt()) 
                    sub1=sc.nextInt();
                else 
                    throw new NumberFormatException();
                    
                
                if(sc.hasNextInt())
                    sub2=sc.nextInt();
                else
                    throw new NumberFormatException();
                
                
                if(sc.hasNextInt())
                    sub3=sc.nextInt();
                else
                    throw new NumberFormatException();
                
                
                if(sub1<0)throw new NegativeValueException();
                if(sub1>100)throw new ValueOutOfRange();
                
                if(sub2<0)throw new NegativeValueException();
                if(sub2>100)throw new ValueOutOfRange();
                
                if(sub3<0)throw new NegativeValueException();
                if(sub3>100)throw new ValueOutOfRange();
                
                avg = (sub1+sub2+sub3)/3;
                System.out.println("Name : "+name[i]);
                System.out.println("Marks in subject 1 : "+sub1);
                System.out.println("Marks in subject 2 : "+sub2);
                System.out.println("Marks in subject 3 : "+sub3);
                System.out.println("Average Marks : "+avg);
                
                }catch(NumberFormatException e) {
                System.out.println(e);
            }catch(NegativeValueException e) {
                System.out.println(e);
            }catch(ValueOutOfRange e) {
                System.out.println(e);
            }
            
            
        }
        
        sc.close();
    }

}

Answer 1

问题出现在读取输入的第一个循环之后，因为在扫描仪 class 的最后一个 scan.nextInt() 方法之后，光标停留在同一条线。因此，当您使用 nextLine() 作为名称时，您的输入将被视为输入，当您输入名称时，它会显示 NFE。 [

要解决这个问题，您可以做的是在完成最后一个整数输入后，使用 nextLine() 处理剩余的行，那么你的代码可以正常工作，

import java.util.Scanner;

@SuppressWarnings("serial")
class NegativeValueException extends Exception {

    public NegativeValueException() {

    }
}

@SuppressWarnings("serial")
class ValueOutOfRange extends Exception {
    public ValueOutOfRange() {
        System.out.println("Value out of range Exception");
    }
}

public class Student1 {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        for (int i = 0; i < 2; i++) {
            String[] name = new String[2];
            int sub1 = 0;
            int sub2 = 0;
            int sub3 = 0;
            double avg;

            try {

                System.out.println("Enter the data of Student " + (i + 1) + " : ");

                name[i] = sc.nextLine();
//              sc.next();
                if (name[i].equals(null))
                    break;
                
                 if (sc.hasNextInt())
                    sub1 = sc.nextInt();
                else
                    throw new NumberFormatException();

                if (sc.hasNextInt())
                    sub2 = sc.nextInt();
                else
                    throw new NumberFormatException();

                if (sc.hasNextInt())
                    sub3 = sc.nextInt();
                else
                    throw new NumberFormatException();

                if (sub1 < 0)
                    throw new NegativeValueException();
                if (sub1 > 100)
                    throw new ValueOutOfRange();

                if (sub2 < 0)
                    throw new NegativeValueException();
                if (sub2 > 100)
                    throw new ValueOutOfRange();

                if (sub3 < 0)
                    throw new NegativeValueException();
                if (sub3 > 100)
                    throw new ValueOutOfRange();

                avg = (sub1 + sub2 + sub3) / 3;
                System.out.println("Name : " + name[i]);
                System.out.println("Marks in subject 1 : " + sub1);
                System.out.println("Marks in subject 2 : " + sub2);
                System.out.println("Marks in subject 3 : " + sub3);
                System.out.println("Average Marks : " + avg);
                sc.nextLine(); // add this 
            } catch (NumberFormatException e) {
                System.out.println(e);
            } catch (NegativeValueException e) {
                System.out.println(e);
            } catch (ValueOutOfRange e) {
                System.out.println(e);
            }

        }

        sc.close();
    }

}

输出为

Enter the data of Student 1 : 
john
12
32
41
Name : john
Marks in subject 1 : 12
Marks in subject 2 : 32
Marks in subject 3 : 41
Average Marks : 28.0
Enter the data of Student 2 : 
jack
12
43
55
Name : jack
Marks in subject 1 : 12
Marks in subject 2 : 43
Marks in subject 3 : 55
Average Marks : 36.0

Answer 2

由于@Gurkirat 已经指出了错误，我只是添加我的答案作为对您代码的改进。

import java.util.Scanner;

    @SuppressWarnings("serial")
    class NegativeValueException extends Exception {
        public  NegativeValueException() {
            System.out.println("Negative Value Exception");       
        }
    }
    @SuppressWarnings("serial")

    class ValueOutOfRange extends Exception {
        public ValueOutOfRange() {
            System.out.println("Value out of range Exception");
        }
    }

    public class Student1 {
        public static void main(String[] args) {
            String[] name = new String[2];
            for(int i=0; i<2; i++) {
                int sub1, sub2, sub3;
                double avg;

                try (Scanner sc = new Scanner(System.in)) {
                    System.out.println("Enter the data of Student "+ (i+1) +" : ");
                    name[i] = sc.nextLine();
                    sub1 = sc.nextInt();
                    sub2 = sc.nextInt();
                    sub3 = sc.nextInt();
                    sc.next(); //Added this to solve your problem.

                    if(sub1 < 0 || sub2 < 0 || sub3 < 0)
                        throw new NegativeValueException();
                    if(sub1 > 100 || sub2 > 100 || sub3 > 100)
                        throw new ValueOutOfRange();
                
                    avg = (sub1+sub2+sub3)/3;
                    System.out.println("Name : " + name[i] + 
                    "\nMarks in subject 1 : " + sub1 +
                    "\nMarks in subject 2 : " + sub2 +
                    "\nMarks in subject 3 : "+sub3 +
                    "\nAverage Marks : " + avg);
                
                 } catch(ValueOutOfRange | NegativeValueException e) {
                    System.out.println(e);
                 }
            }
        
    }

}

我的代码中出现 NameFormatException 并且跳过了代码的特定部分？

I am getting NameFormatException in my code and a certain part of code is being skipped?

java

exception

numberformatexception