Question

我对Java很新，所以我确信我的代码非常丑陋和基本。我试图了解如何使用构造函数，setter和getter。我曾尝试查看本网站上的其他问题，查看视频，阅读本书。这对我来说很难理解。任何人都可以帮助我吗？

以下是我的完整代码。我必须为项目使用setter和getter，我想确保我非常了解它们。

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

正确定义了setter和getter。您的问题出在main方法中，您可以将setter调用为静态方法：

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

您应该在您的实例上调用它们：

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

难以理解构造函数，setter和getter，Java

1 个答案: