Trace Execution and inheritance java

Question

I am new to Java. How can I trace the execution of this program? Does this program convey inheritance correctly or does it just convey a normal encapsulation without inheritance?

I'm just wondering if I really did convey inheritance in these classes. Your responses are much appreciated.

This is the first class, TestMembers:

public class TestMembers {

    public static void main (String args []){

        Members Ailee=new Members("Ailee","52213116028","BRS",2,1.6,45);
        Members Amy=new Members("Amy","52213116032","BDR",2,1.63,57);
        Members Jack=new Members("Jack","52213116201","BRE",2,1.75,82);

        String[] member = { "Ailee","Amy", "Jack"};
        JFrame frame = new JFrame();
        String teammembers = (String) JOptionPane.showInputDialog(frame, "Team 
        Members","Team members",
        JOptionPane.QUESTION_MESSAGE,null,member, member[0]);

        if (teammembers==member[0]){
            JOptionPane.showMessageDialog(null,Ailee,"Member Profile", 
            JOptionPane.INFORMATION_MESSAGE);
        } else if (teammembers==member[1]){
            JOptionPane.showMessageDialog(null,Amy,"Member Profile", 
            JOptionPane.INFORMATION_MESSAGE);
        } else if (teammembers==member[2]){
            JOptionPane.showMessageDialog(null,Jack,"Member Profile", 
            JOptionPane.INFORMATION_MESSAGE);
        }
        System.exit(0);
    }
}

This is the other class, Person:

public class Person {

    private String name;
    private double height;
    private double weight;

    public void setPersonname(String name){
        this.name=name;
    }

    public String getPersonname(){
        return name;
    }

    public void setPersonHeight(double height){
        this.height=height;
    }

    public double getPersonHeight(){
        return height;
    }

    public void setPersonWeight(double weight){
        this.weight=weight;
    }

    public double getPersonWeight(){
        return weight;
    }
}

This is the third class, Student:

public class Student extends Person{

    private String id_number;
    private String course;
    private int semester;

    public void setStudentIdNumber(String id_number){
        this.id_number=id_number;
    }

    public String getStudentIdNumber(){
        return id_number;
    }

    public void setStudentCourse(String course){
        this.course=course;
    }

    public String getStudentCourse(){
        return course;
    }

    public void setStudentSemester(int semester){
        this.semester=semester;
    }

    public int getStudentSemester(){
        return semester;
    }
}

This is the fourth class, Members:

public class Members extends Student{

    private double bmi;
    private String bmistatus;

    public Members(String name,String id_number, String course, int semester, 
        double height, double weight){
        setPersonname(name);
        setStudentIdNumber(id_number);
        setStudentCourse(course);
        setStudentSemester(semester);
        setPersonHeight(height);
        setPersonWeight(weight);
    }

    public double getMemberBMI(){
        bmi= getPersonWeight()/(getPersonHeight()*getPersonHeight());
        DecimalFormat twoDForm = new DecimalFormat("#.00");
        return Double.valueOf(twoDForm.format(bmi));
    }

    public String BMIstatus(){
        if (bmi>= 18.5 & bmi <= 25.0){
            return bmistatus= "Optimal weight";
        } else if (bmi<18.5){
            return bmistatus="Underweight";
        } else if (bmi>25.0){
            return bmistatus="Overweight";
        }
        return bmistatus;
    }

    public String toString() {
        return "Name: " + getPersonname() + "\nID: " + getStudentIdNumber() 
        +"\nCourse: 
        " + getStudentCourse()+
        "\nSem: " + getStudentSemester()+"\nHeight: "+getPersonHeight()+" metre"+
        "\nWeight: "+getPersonWeight()+" kg"+"\nBMI:"+getMemberBMI()+"\nBMI         status 
        :"+BMIstatus();
    }
}

Answer 1

I think, inheritance is - syntactically - correct. From design point of view, it depends on a wider context.

Regarding software design, there is no easy way to learn it. You might want to read books on Clean Code, Refactoring or Design Patterns (in this order). They will teach you lots of ground rules. However, you need to learn from your day job too, so you can learn how to apply these rules.

About tracing, you can use either a Logger, or simply System.out, e.g.:

private static final Logger logger = Logger.getInstance(TestMembers.class);
...
if (teammembers==member[0]) {
    logger.debug("first member");
}
...

Also, I suggest to remove the trailing System.exit(0); There are other ways to do this.