Package not working with object creation in simple program

[William Golovlev]

Hi, my simple program is not working. I created the package with the Student file within by using javac -d . Student.java after compiling it. Then, the ThisDemo class does not compile. I did some debugging and found issues, but still getting the exact same errors.

import test1.Student;

public class ThisDemo {
	public static void main(String args[]) { 
	Student international_student = new Student(10585, "Julius Caesar", "Athens", 'I');
	Student highschool_student = new Student(10678, "James Brown", "Oakland", 'H');

	international_student.print();
	highschool_student.print();
	}
}

package test1;

public class Student{
    private int id;
    private String name;
    private String city;
    private char dual_enrolled;

    Student(int id, String name, String city, char dual_enrolled) { // ID, Name, City, International or High School
        this.id = id;
        this.name = name;
        this.city = city;
        this.dual_enrolled = dual_enrolled;
    }

    public void print() {                 // method will output Name, ID, City, Enrollment Status
        System.out.println(id + " " + name
            + " " + city + " " + dual_enrolled);
    }
}

Just to reiterate- Student.java compiled fine, then I made test1 package with Student inside of it. After that, well, nothing works.

EDIT for console error:

C:\Users\Will\mywork>javac ThisDemo.java
ThisDemo.java:5: error: Student(int,String,String,char) is not public in Student; cannot be accessed from outside package
        Student international_student = new Student(10585, "Julius Caesar", "Athens", 'I');
                                        ^
ThisDemo.java:6: error: Student(int,String,String,char) is not public in Student; cannot be accessed from outside package
        Student highschool_student = new Student(10678, "James Brown", "Oakland", 'H');
                                     ^
2 errors

C:\Users\Will\mywork>javac -d . Student.java

C:\Users\Will\mywork>java Student.java
error: can't find main(String[]) method in class: test1.Student

C:\Users\Will\mywork>java ThisDemo
Error: Could not find or load main class ThisDemo
Caused by: java.lang.ClassNotFoundException: ThisDemo

The student not having main when being run was my mistake since it has no main, and the I forgot brackets for ThisDemo after args- but the other errors baffle me.

[Norm Radder]

getting the exact same errors.

Please copy the full text of the error messages and paste it here so we can see what problems you are having.

[William Golovlev]

Norm Radder wrote:

getting the exact same errors.

Please copy the full text of the error messages and paste it here so we can see what problems you are having.

whoops, edited.

[Campbell Ritchie]

William Golovlev wrote:. . . whoops, edited.

Please don't edit posts like that; it makes it appear that Norm was mistaken.

The error message you showed proves that the package structure isn't the problem. It is that the constructor you are calling has package‑private (=default) access; it is only accessible from the main() method if you give it public access.

Please only use _ in identifiers in,

1: Package names, as described in the Java™ Tutorials, and

2: Constant names ALL_IN_UPPER_CASE.

Other identifiers should be written inMixedCase.

[William Golovlev]

My professor put up code that purposefully is wrong, so there are errors I am still working with. I forgot a constructor must be declared as public, but after putting the public access modifier, I Still get this after saving, deleting the package and recompiling it-

C:\Users\Will\mywork>javac Student.java

C:\Users\Will\mywork>javac -d . Student.java

C:\Users\Will\mywork>javac ThisDemo.java
ThisDemo.java:5: error: Student(int,String,String,char) is not public in Student; cannot be accessed from outside package
        Student international_student = new Student(10585, "Julius Caesar", "Athens", 'I');
                                        ^
ThisDemo.java:6: error: Student(int,String,String,char) is not public in Student; cannot be accessed from outside package
        Student highschool_student = new Student(10678, "James Brown", "Oakland", 'H');
                                     ^
2 errors

C:\Users\Will\mywork>

[Norm Radder]

is not public in Student

Check that the Student class's constructor is public.  Make sure there are not old versions around.

[Tim Holloway]

Your file locations are wrong. Java package/directory rules require that the compiler should output file test1/Student.class Preferably the compile source would be file test1/Student.java.

Also, your error message comes from the fact (as Campbell said) that you did not declare the constructor for Student to be public, so it defaulted to package scope. One of Java's quirkier features.

[Campbell Ritchie]

Tim Holloway wrote:. . . . One of Java's quirkier features.

There are worse features. Some of the worst have been deprecated.

[Campbell Ritchie]

William Golovlev wrote:. . . a constructor must be declared as public

That isn't correct. A constructor or class member must be public in order to be accessible from different classes or objects outside the package. You need such access.

My professor put up code that purposefully is wrong, so there are errors I am still working with. . . .

Does that include using a char for status?The compiler won't notice, but I did.

Please don't quote the whole of the preceding post; such quotes are liable to removal without notice.

[William Golovlev]

Ok well I am not quite sure why this is an issue because I have made my file contain a public constructor..

package test1;

public class Student{
    private int id;
    private String name;
    private String city;
    private char dual_enrolled;

    public Student(int id, String name, String city, char dual_enrolled) { // ID, Name, City, International or High School
        this.id = id;
        this.name = name;
        this.city = city;
        this.dual_enrolled = dual_enrolled;
    }

    public void print() {                 // method will output Name, ID, City, Enrollment Status
        System.out.println(id + " " + name
            + " " + city + " " + dual_enrolled);
    }
}

Not sure if file locations are causing the issue, I have a mywork folder with all my work, then Student is in test1 folder (package) within the mywork folder.

C:\Users\Will\mywork>javac ThisDemo.java
ThisDemo.java:5: error: Student(int,String,String,char) is not public in Student; cannot be accessed from outside package
        Student international_student = new Student(10585, "Julius Caesar", "Athens", 'I');
                                        ^
ThisDemo.java:6: error: Student(int,String,String,char) is not public in Student; cannot be accessed from outside package
        Student highschool_student = new Student(10678, "James Brown", "Oakland", 'H');
                                     ^
2 errors

[Norm Radder]

Are there any old versions of the Student class file around?

[Campbell Ritchie]

...and please show us the directory structure you are working in. There is something we don't know about yet.

[William Golovlev]

William Golovlev wrote:Ok well I am not quite sure why this is an issue because I have made my file contain a public constructor..

Update: never was an issue with the code. For some reason I was compiling, and everytime I compiled it was not re-compiling the file in my package folder. Thought I was doing it right with "java -d . ThisDemo.java" but deleting all class files and recompiling worked. Thanks!

[Campbell Ritchie]

Well done and thank you for explaining the solution.