使用java集合排序Person的ArrayList

Question

下面我使用的代码工作正常，并输出名称，但排序方法不起作用。我需要“Collections.sort（nameFromText）；”按名字的字母顺序对ArrayList排序。

我做错了什么？

public static void main(String[] args) throws IOException {
    // Create and populate text file
    Writer textFile = new FileWriter("names.txt");
    String[] nameArray = new String[] { "Tina Tully\n", "Bill Simpson\n",
            "Dana Smith\n", "Ralph Andrews\n", "Greg Smithers\n",
            "Lisa Krump\n", "Gill Bitters\n", "Barbara West\n",
            "Sandra McDonald\n", "Bart Willis\n", "Bucky Zimmerman\n",
            "Richard Vicks\n", "Velma Tarp\n", "Winslow Tunnell\n",
            "Andrew Letterman\n", "Betty Trump\n", "Waldo Smith\n",
            "Kyle Ronno\n", "Vivian West\n", "Wendy Tunnell\n" };
    generateText(textFile, nameArray);

    // Create object of previously created text file
    Scanner pullFile = new Scanner(new File("names.txt"));

    // Create 20 Person Objects and add to ArrayList data structure with
    // name variables assigned to values from text file
    ArrayList<Person> nameFromText = new ArrayList<Person>();
    fillArrayList(nameFromText, pullFile);

    // Sort ArrayList
    Collections.sort(nameFromText);

    // Print ArrayList
    printNamesFromObjects(nameFromText);
}

private static void printNamesFromObjects(ArrayList<Person> namesFromText) {
    for (int i = 0; i < 20; i++) {
        System.out.println(namesFromText.get(i).name);
    }
}

private static void fillArrayList(ArrayList<Person> nameFromText,
        Scanner pullFile) {
    while (pullFile.hasNext()) {
        Person obj = new Person(pullFile.nextLine());
        nameFromText.add(obj);
    }
}

private static void generateText(Writer textFile, String[] nameArray)
        throws IOException {
    for (int i = 0; i < 20; i++) {
        textFile.write(new String(nameArray[i]));
    }
    textFile.close();
}

Answer 1

试试这个：

List<String> inputString =  Arrays.asList("Sijan", "Sudeep", "Parasar", "Raj Kumar");
Collections.sort(inputString);
System.out.println(inputString);

Answer 2

或者，您可以直接在Person类中实现Compariable接口，并重写“compareTo（Object obj）”方法。在这种情况下，您不需要为comparator创建新类。这就像内置排序一样。

Answer 3

<代码>集合。排序（列表

在下面的代码中，您不满足上述两个条件。您的Person类既没有实现Compariable，也没有传递任何Compariator实例。

ArrayList<Person> nameFromText = new ArrayList<Person>();
fillArrayList(nameFromText, pullFile);
// Sort ArrayList
Collections.sort(nameFromText);  // How to sort?

您应该为您的Person类创建一个比较器，以告诉ort（）方法如何对其进行排序（可能在存储在Person类中的String上）

下面是如何实现通用比较器：

public class PersonNameComparator implements Comparator<Person> {
    public int compare(Person p1, Person p2) {
        return p1.getName().compareTo(p2.getName());
    }
}

然后是您的集合。sort（）方法调用应类似于：-

Collections.sort(nameFromText, new PersonNameComparator());