在线程“ main” java.lang.NoClassDefFoundError中使用程序包“ Exception”时出现奇怪的错误。 ”

Question

I get "Exception in thread "main" java.lang.NoClassDefFoundError" while using "package"

1. if I comment "//package com.kevin.corejava; " it would run successfully;
2. Or, I delete the "main" method in "Employee.java", and add a class "Test.java" in folder "E:\\Space\\java" which imports "Employee.java" (import com.kevin.corejava.*), and reference Employee int its main method, it would still run successfully.

Why the "main" method in Employee could not run by itself when I add the sentence "package com.kevin.corejava" (Employee.java is put in path E:\\Space\\java\\com\\kevin\\corejava\\Employee.java)

package com.kevin.corejava;
import java.util.*;
import static java.lang.System.*;

public class Employee
{
    public Employee(String n, double s, int year, int month, int day)
    {
        name = n;
        salary = s;
        GregorianCalendar calendar = new GregorianCalendar(year, month-1,day);
        hireDay = calendar.getTime();
    }

    public String getName()
    {
        return name;
    }

    public double getSalary()
    {
        return salary;
    }
    public Date getHireDay()
    {
        return hireDay;
    }
    public void raiseSalary(double byPercent)
    {
        double raise = salary *byPercent/100;
        salary+=raise;
    }

    private String name;
    private double salary;
    private Date hireDay;


    public static void main(String[] args)
    {
        System.out.println("This is main ,I won't say 'Hello World'!");
    }

}

Answer 1

Just make sure you follow the below things :

1. "package com.kevin.corejava;" It should be a valid path.

2. Your package path must be executed by JDK, and JRE must access its class file. (Make Sure your JDK and JRE paths are right to access this file).

3. The class name must be same as the file name as the main method is in your Employee class.

4. Your project's Build path is right. If you use Eclipse or other IDE, just right click and configure your build path.