如何使用链表中的对象

Question

我正在使用链表进行作业，但我对某些事情感到困惑。我们必须为电话簿创建另一个 class，它接收姓名和号码，然后将其存储在链表中，我已经弄清楚了其中的大部分内容。直到我开始尝试从链表中取出 person 对象，这样我就可以运行我为 person 对象编写的方法，比如 getter 和 setter 等等。但是当我把它从链表中拉回来的时候，它只是一个对象，而不是我放入的人，请问如何把这个对象拉出来，这样我才能把它当作我放入的对象。谢谢

好的，很抱歉将其添加到评论中。这是我到目前为止尝试过的测试，人 class 有一个打印方法，但我忘了用

分配类型

public static void main(String[] args) {      
    LinkedList phonedir = new LinkedList();
    person one = new person("John", "Doe", "1234567890");
    phonedir.add(one);
    Object two = phonedir.get(0);
    two.print();
}

Answer 1

你应该使用LinkedList<person>这样编译器就知道你得到的是一个person.

public static void main(String[] args) {
    LinkedList<person> phonedir = new LinkedList<person>(); 
    person one = new person("John", "Doe", "1234567890"); 
    phonedir.add(one); 
    person two = phonedir.get(0); 
    two.print(); 
}

另外，应该是Person。 Class Java 中的名称应以大写字母开头！

Answer 2

public class SaveRetrieveObjects {
    List<Item>  objs        = new LinkedList<Item>();
    File        fileName    = new File("objects.sav");

public SaveRetrieveObjects() {
    createItems();
    showItems();
    serializeObjs(objs, fileName);
    objs = deserializeObjs(objs, fileName);
    showItems();
    System.out.println("Vale!");
}

private void createItems() {
    Item oneObject = new Item();
    oneObject.setId("Citric-45");
    oneObject.setDesc("orange");
    oneObject.setCost(12345.67);
    oneObject.setQty(67);
    oneObject.setBool(true);
    oneObject.setColor(Color.orange);
    objs.add(oneObject);

    oneObject = new Item();
    oneObject.setId("Mobil-12");
    oneObject.setDesc("car");
    oneObject.setCost(67890.12);
    oneObject.setQty(2);
    oneObject.setBool(true);
    oneObject.setColor(new Color(1, 2, 3));
    objs.add(oneObject);
}

private void showItems() {
    Item itm;
    for (int j = 0; j < objs.size(); j++) {
        itm = objs.get(j);
        System.out.println("Item " + (j + 1) + " Contents:");
        System.out.print("\t" + itm.getId());
        System.out.print("\t" + itm.getDesc());
        System.out.print("\t" + itm.getCost());
        System.out.print("\t\t" + itm.getQty());
        System.out.println("\t" + itm.isBool());
        System.out.println("\t" + itm.getColor());
    }
     System.out.println("----------------------------------------------------");
}

private void serializeObjs(List<Item> objs, File file) {
    System.out.println("Serialization process started");
    FileOutputStream fos = null;
    ObjectOutputStream oos = null;
    try {
        fos = new FileOutputStream(file);
        oos = new ObjectOutputStream(fos);
        oos.writeObject(objs);
    } catch (FileNotFoundException e) {
        System.out.println(e.getMessage());
    } catch (IOException e) {
        System.out.println(e.getMessage());
    } finally {
        try {
            oos.close();
            fos.close();
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }
    System.out.println("\nSerialization ended successfully");
    System.out.println("Checkout your specified output file");
    System.out.println("-----------------------------------");
}

@SuppressWarnings("unchecked")
private List<Item> deserializeObjs(List<Item> objs, File file) {
    objs.clear();
    System.out.println("Deserialization process started");
    FileInputStream fis = null;
    ObjectInputStream ois = null;
    try {
        fis = new FileInputStream(file);
        ois = new ObjectInputStream(fis);
        objs.addAll((Collection<? extends Item>) ois.readObject());
    } catch (FileNotFoundException e) {
        System.out.println(e.getMessage());
    } catch (IOException e) {
        System.out.println(e.getMessage());
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } finally {
        try {
            ois.close();
            fis.close();
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }
    System.out.println("Deserialization process ended");
    return objs;
}

public static void main(String[] args) {
    javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            new SaveRetrieveObjects();
        }
    });
}
}

class Item implements Serializable {
private static final long   serialVersionUID    = 1L;

private String                      id;
private String                      desc;
private double                      cost;
private int                             qty;
private boolean                     bool;
private Color                           color;

public Item() {
    id = "";
    desc = "";
    cost = 0;
    qty = 0;
    bool = false;
    color = new Color(0, 0, 0);
}

public Item(String id, String desc, double cost, int qty, boolean bool, Color color) {
    this.id = id;
    this.desc = desc;
    this.cost = cost;
    this.qty = qty;
    this.bool = bool;
    this.color = color;
}

public String getId() {
    return id;
}

public void setId(String itemID) {
    this.id = itemID;
}

public String getDesc() {
    return desc;
}

public void setDesc(String desc) {
    this.desc = desc;
}

public double getCost() {
    return cost;
}

public void setCost(double cost) {
    this.cost = cost;
}

public int getQty() {
    return qty;
}

public void setQty(int quantity) {
    this.qty = quantity;
}

public boolean isBool() {
    return bool;
}

public void setBool(boolean bool) {
    this.bool = bool;
}

public Color getColor() {
    return color;
}

public void setColor(Color color) {
    this.color = color;
}
}

这是 "How to use Objects from a Linked List" 上的完整示例。
在 LinkedList 或 ArrayList 中使用对象：
步骤：
* -Create Class Item implements Serializable.
* - 创建项目对象。
* - 将它们添加到 ArrayList 或 LinkedList。这些，ArrayList 或 LinkedList，做不需要可序列化！只有项目 class 需要实施可序列化。
* - 使用流在所选文件中写入和检索对象。
希望这对其他人有所帮助。淡水河谷！

如何使用链表中的对象

How to use the object from a Linked List

java

linked-list