Trouble understanding constructors, setters, and getters, Java

Question

I'm fairly new to Java, so I am sure that my code is very ugly and basic. I am trying to understand how to use constructors, setters, and getters. I've tried looking at other questions on this site, looking at videos, reading the book. It's just difficult for me to understand. Can anyone help me?

Below is my code in full. I have to use setters and getters for a project, and I want to make sure I understand them very well.

import javax.swing.JOptionPane;

public class userCar {

  private int carYear;
  private int speed; 
  private String make;

  public void setCarYear(int carYear){
    this.carYear=carYear;
  }

  public void setCarSpeed(int speed){
    this.speed=speed;
  }

  public void setCarMake(String make){
    this.make=make;
  }

  public int getCarYear(){
    return this.carYear;    
  }

  public int getCarSpeed(){
    return this.speed;    
  }

  public String getCarMake(){
    return this.make;   
  }



  public static void main (String [] args){

    userCar ourCar = new userCar();

    String userCarInput []= new String[3];

    userCarInput= carInfo();

    //THIS IS AN ERROR---
    //"Cannot make a static reference to the non-static method setCarYear(int) from the type  
    //userCar"

    userCar.setCarYear(Integer.parseInt(userCarInput[0]));
    userCar.setCarSpeed(Integer.parseInt(userCarInput[2]));
    userCar.setCarMake(userCarInput[1]);


    //This would be displaying the the car make, year, and speed (using the get methods) but I am 
    //currently testing to make sure the values are correct. The array works fine, but not the    
    //setter/getter 

    JOptionPane.showMessageDialog(null,ourCar.getCarMake()+".\n"+ userCarInput[1]+".\n" + 
        userCarInput[2] +".\n");

  }


  public static String[] carInfo(){
    String stringSpeed, stringYear, stringMake ;

    String carInformation[] = new String[3];


    stringSpeed=JOptionPane.showInputDialog("What is the speed of the car in MPH?");

    //Deals with blank or "bad" entries. Follows in stringYear and stringMake as well.
    if (stringSpeed == null) {
      System.exit(0); }
    while (stringSpeed.trim().length()== 0 || Integer.parseInt(stringSpeed) < 0){
      stringSpeed= JOptionPane.showInputDialog("You did not enter a valid value.\n" +
          "Please enter a valid value for speed.");
      if (stringSpeed == null){
        System.exit(0);} 
    }//ends the while


    stringMake=JOptionPane.showInputDialog("What is the make of the car? [Toyota, "
        + "Cadillac, etc.] ");

    if (stringMake == null) {
      System.exit(0); }
    while (stringMake.trim().length()== 0){
      stringSpeed= JOptionPane.showInputDialog("You did not enter a valid value.\n" +
          "Please enter a valid value for the car's make.");
      if (stringSpeed == null){
        System.exit(0);} 
    }//ends the while


    stringYear=JOptionPane.showInputDialog("What year was the car made?");

    if (stringYear == null) {
      System.exit(0); }
    while (stringYear.trim().length()== 0 || Integer.parseInt(stringYear) < 1769 ||
        Integer.parseInt(stringYear) > 2016){
      stringYear= JOptionPane.showInputDialog("You entered "+ stringYear + ".\n" +
          "The first car was made in 1769, and the latest model is a 2015.\n"
          +"Please enter a valid value for the car's year.");
      if (stringYear == null){
        System.exit(0);} 
    }//ends the while

    carInformation [0] = stringSpeed;
    carInformation [1] = stringMake;
    carInformation [2] = stringYear;

    return carInformation;
  }


}

Answer 1

The setters and getter are defined properly. Your problem is in the main method, where you call the setters as if they are static methods :

userCar.setCarYear(Integer.parseInt(userCarInput[0]));
userCar.setCarSpeed(Integer.parseInt(userCarInput[2]));
userCar.setCarMake(userCarInput[1]);

You should call them on your instance :

ourCar.setCarYear(Integer.parseInt(userCarInput[0]));
ourCar.setCarSpeed(Integer.parseInt(userCarInput[2]));
ourCar.setCarMake(userCarInput[1]);