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Thread: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

  1. #1
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    Default Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    Hi, I have a super class Person and its sub class Student. Student has a toString method that prints out the details of the Student object including the first name. But I keep getting the error described in the title. Is there another way to fix this problem without making the method static?

    Person super class
    public class Person
    {
        private String firstName, lastName, id;
     
        /**
         * Creates a Person object.
         * 
         * @param firstName the first name of the Person
         * @param lastName the last name of the Person
         * @param id the id number of the Person
         */
        public Person(String firstName, String lastName, String id) {
            this.firstName=firstName;
            this.lastName=lastName;
            this.id=id;
        }
     
        /**
    	 * Returns the first name.
    	 * 
    	 * @return the firstName
    	 */
    	public String getFirstName() {
    		return firstName;
    	}
     
    	/**
    	 * Sets the first name.
    	 * 
    	 * @param firstName the firstName to set
    	 */
    	public void setFirstName(String firstName) {
    		this.firstName = firstName;
    	}
     
    	/**
    	 * Returns the last name.
    	 * 
    	 * @return the lastName
    	 */
    	public String getLastName() {
    		return lastName;
    	}
     
    	/**
    	 * Sets the last name.
    	 * 
    	 * @param lastName the lastName to set
    	 */
    	public void setLastName(String lastName) {
    		this.lastName = lastName;
    	}
     
    	/**
    	 * Returns the id.
    	 * 
    	 * @return the id
    	 */
    	public String getId() {
    		return id;
    	}
    }

    Student sub class:
     
    import java.util.ArrayList;
     
     
    public class Student extends Person {
     
    	private double gpa;
    	private ArrayList<CourseAttempted> transcript;
    	private int creditsCompleted;
     
    	/**
    	 * Creates a student.
    	 * 
    	 * @param firstName the first name of the student
    	 * @param lastName the last name of the student
    	 * @param id the student's id
    	 */
    	public Student(String firstName, String lastName, String id) {
    		super(firstName, lastName, id);
    		gpa = 0.0;
    		transcript = new ArrayList<CourseAttempted> ();
    		creditsCompleted = 0;
    		}
     
    	/**
    	 * @return the gpa
    	 */
    	public double getGpa() {
    		return gpa;
    	}
     
    	/**
    	 * Adds a course to the student's transcript.
    	 * 
    	 * @param courseToAdd the course to add
    	 */
     
    	public void addCourse(Course c, String semester, int year, double grade) {
    	    CourseAttempted courseToAdd = new CourseAttempted(c, semester, year, grade);
    	    transcript.add(courseToAdd);
     
    		// the total number of credits attempted is the sum of
    		// creditsCompleted and the number of credits of the course to be added
    		// to the transcript
    		int creditsAttempted = courseToAdd.course.getCredits() + creditsCompleted;
     
    		// gpa is computed by doing the following:
    		// for each course attempted, multiply the number of credits by the
    		// course grade.  
    		// gpa is the sum of the above for all the courses divided by the
    		// number of total credits
    		// 
    		double currentPoints = gpa * creditsCompleted + courseToAdd.grade * 
    		                        courseToAdd.course.getCredits();
     
    		gpa = currentPoints / creditsAttempted;
     
    		if (courseToAdd.grade > 0) 
    		   creditsCompleted += courseToAdd.course.getCredits();
    	}
     
    	/**
        * Returns the list of courses as a String.
        * 
        * @return the list of courses the student has taken
        */
        public String getTranscript() {
            String courseList = "";
     
            for (CourseAttempted ca: transcript) 
                courseList = courseList + ca + "\n";
     
            return courseList;
        }
     
    	/**
    	 * Returns a String representation of a Student
    	 * 
    	 * @return a string representing the student
    	 */
    	public String toString() {
    		String s = this.getClass().getName().toUpperCase() + ":\t" + Person.getFirstName() + " " + lastName 
    				+ "\tID = " + id + "\tGPA = " + gpa + "\tCredits Completed = " + creditsCompleted;
    		s += "\nHere are all the courses the student has taken so far";
    		s += "\n-----------------------------------------------------";
    		s += "\n" + getTranscript();
            return s;
        }	
    }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    A toString() method definitely should not be static.

    When you call the toString() method, use a reference to the class, not the name of the class.
    Using the class's name means it's a call to a static method.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    I'm talking about changing the getFirstName() method to static not the toString() method. I cant call the toString() because I can't even compile the student class.

  4. #4
    Super Moderator Norm's Avatar
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    Default Re: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    Don't make any of the methods static. Use references to the class object to call a class's methods.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    So are you saying I should create a person object within my Person class to be able to call methods from that class?
    Like:
    Person p = new Person("Joe", "Smith", "0394857");

    To call p.getFirstName();?

  6. #6
    Super Moderator Norm's Avatar
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    Default Re: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    You do NOT need a reference to the class to call other methods of the same class. There is an implied this reference added by the compiler. Just code the method name without any object reference.
    If you don't understand my answer, don't ignore it, ask a question.

  7. The Following User Says Thank You to Norm For This Useful Post:

    EDale (May 3rd, 2013)

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    Default Re: Error message non-static method Person.getFirstName() cannot be referenced from a static context?

    I got it. Thank you so much! This was my last programming assignment of the semester. So glad it's over!

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