java - 如何使用 toString 和 getter 和 setter 方法

Question

我按照以下说明乘坐奋斗巴士。我不知道如何使用 toString() 方法来打印我的数据值。我也不知道如何将颜色打印为表示“黑色”或“蓝色”的字符串。而且我不知道如何使用 boolean 值来表示“已连接”或“已断开连接”。

Create a Java class named HeadPhone to represent a headphone set. The class contains:

• Three constants named LOW, MEDIUM and HIGH with values of 1, 2 and 3 to denote the headphone volume.

• A private int data field named volume that specifies the volume of the headphone. The default volume is MEDIUM.

• A private boolean data field named pluggedIn that specifies if the headphone is plugged in. The default value if false.

• A private String data field named manufacturer that specifies the name of the manufacturer of the headphones.

• A private Color data field named headPhoneColor that specifies the color of the headphones.

• getter and setter methods for all data fields.

• A no argument constructor that creates a default headphone.

• A method named toString() that returns a string describing the current field values of the headphones.

• A method named changeVolume(value) that changes the volume of the headphone to the value passed into the method

Create a TestHeadPhone class that constructs at least 3 HeadPhone objects.

public class TestHeadPhone {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // construct an object
        HeadPhone headPhone = new HeadPhone();

        System.out.println("Manufacturer: " + headPhone.getManufacturer());
        System.out.println("Color: " + headPhone.getColor());
        System.out.println("Currently: " + headPhone.getStatus());
        System.out.println("Volume: " + headPhone.getVolume());
        if(headPhone.getStatus() == false){
            System.out.println("Please plug the Head Phones into a device.");   
        }

        headPhone.setNewHeadphone();

        System.out.println("\n" + "Manufacturer: " + 
            headPhone.getManufacturer());
        System.out.println("Color: " + headPhone.getColor());
        System.out.println("Currently: " + headPhone.getStatus());
        System.out.println("Volume: " + headPhone.getVolume());
        if(headPhone.getStatus() == true){
            System.out.println("Currently playing classical music.");   
        }

    }

}

package testheadphone;
// import color class
import java.awt.Color;

/**
 *
 * @author 
 */
public class HeadPhone {
    // class variables
    private static final int LOW = 1;
    private static final int MEDIUM = 2;
    private static final int HIGH = 3;
    private int volume = MEDIUM;
    private boolean pluggedIn = false;
    private String manufacturer;
    private Color headPhoneColor;

    //default constructor method
    public HeadPhone(){
        this.manufacturer = "Bose";
        this.headPhoneColor = Color.black;
        this.volume = MEDIUM;
        this.pluggedIn = false;       
    } // end default constructor
    // getter method
    public String getManufacturer(){
        return manufacturer;
    }
    // getter method
    public Color getColor(){
        return headPhoneColor;
    }
    // getter method
    public int getVolume(){
        return volume;
    }
    // getter method
    public boolean getStatus(){
        return pluggedIn;
    }   

    public int changeVolume(int change){
        volume = change;
        return volume;
    }
    // setter method
    public void setNewHeadphone(){
        manufacturer = "JVC";
        headPhoneColor = Color.blue;
        pluggedIn = true;
        volume = HIGH;
    }

  //  @Override
  //  public String toString(){
  //      return "Head Phone 1 has the folllowing parameters: " + "\n" + 
  //              "Manufacturer: " + this.manufacturer + "\n" + "Color: Black" + 
  //              "\n" + "Volume is set to: " + this.volume + "\n" + 
  //              "Currently: disconnected" + "\n" + "Please plug the Head Phone"
  //              + " into a device"; 
  //  }

}

我的输出:制造商:Bose颜色:java.awt.Color[r=0, g=0, b=0]当前:错误体积:2请将耳机插入设备。

制造商:JVC颜色:java.awt.Color[r=0,g=0,b=255]目前:真实体积:3目前正在播放古典音乐。

要求的输出:制造商:Bose颜色:黑色当前:断开连接音量设置为:中等请将耳机插入设备。

Head Phone 2 具有以下参数:制造商:JVC颜色:蓝色当前:已连接音量设置为:低当前播放古典音乐播放列表

Answer 1

您可以覆盖要打印的对象的 toString() 方法。然而，一些对象已经以人类可读的格式为您实现了它们的 toString() 方法。即 Color 类。

    ...
    System.out.println("Color: " + headPhone.getColor().toString());
    ...

另一方面，您可以通过重写来自由指定对象应显示为 String 的格式。 (除非对可以/不能修改的内容有类限制，即 final 关键字。)