“线程“主”中的异常 java.lang.NoSuchFieldError：”

Question

I am getting this error:

Exception in thread "main" java.lang.NoSuchFieldError: num1 at calificacion.main(problema_3.java:17)

after type the first value on this simple terminal java program:

import java.io.*;

class num
{
int num1,num2,num3;
}

class calificacion
{
public static void main(String []Args)throws IOException
{
BufferedReader ob1=new BufferedReader(new InputStreamReader (System.in));
num DQ = new num();

System.out.println ("Ingrese primera calificación:");
DQ.num1 = Integer.parseInt(ob1.readLine());
System.out.println ("Ingrese segunda calificación:");
DQ.num2 = Integer.parseInt(ob1.readLine());
System.out.println ("Ingrese tercera calificación:");
DQ.num3 = Integer.parseInt(ob1.readLine());

System.out.println("\n\n");
System.out.println("Calificación final: "+(DQ.num1+DQ.num2+DQ.num3)/3);

}
}

on the other hand this one runs just fine and I am using the same input method in both:

import java.io.*;

class num
{
int numero;
}

class paroimpar
{
public static void main(String []Args)throws IOException
{
BufferedReader ob1=new BufferedReader(new InputStreamReader (System.in));
num DQ = new num();

System.out.println ("Ingrese un número entero para determinar si es par o impar:");
DQ.numero = Integer.parseInt(ob1.readLine());
System.out.println("\n\n");

if (DQ.numero%2==0){
System.out.println(DQ.numero+" es par.");
} else {
System.out.println(DQ.numero+" es impar.");
}
}
}

Thanks in advance.

Answer 1

As You can read here this error states that You're missing field num1 . There is short Baeldung tutorial regarding NoSuchFieldException .

About Your issue. It's not because of the code (I've successfully compiled and run that). I believe it's because of compilation. Do you have those classes in the same directory? During compilation javac calification.java there should be two files out calification.class and num.class . When You compile the second one it may override num.class .

How to solve this issue?

• use different directories / packages
• change one of the num classes names so they don't interfere

BTW. In Java we tend to start classes names with capital letter and variables with camelCase, so it's easier to read:)

Hope it helps! Happy coding!