按字母顺序排序java中的输出文件-Alphabeticallysortingoutputfileinjava

1  

Assuming you have a Person class as follows:

假设您有一个Person类，如下所示：

public class Person {
   private int id;
   private String firstName;
   private String lastName;

   public int getId() {
       return id;
   }
   public void setId(int id) {
       this.id = id;
   }
   public String getFirstName() {
       return firstName;
   }
   public void setFirstName(String firstName) {
       this.firstName = firstName;
   }
   public String getLastName() {
       return lastName;
   }
   public void setLastName(String lastName) {
       this.lastName = lastName;
   }

   public Person(int id, String firstName, String lastName) {
       super();
       this.id = id;
       this.firstName = firstName;
       this.lastName = lastName;
   }
}

you can sort the list of Person objects using the static sort method of Collections as shown below:

您可以使用Collections的静态排序方法对Person对象列表进行排序，如下所示：

    List persOns= new ArrayList();
    persons.add(new Person(1, "John", "Smith"));
    persons.add(new Person(2, "Joe", "Blow"));
    persons.add(new Person(3, "Cat", "Dog"));

    Collections.sort(persons, new Comparator() {
        public int compare(Person p1, Person p2) {
            String lastName1 = p1.getLastName();
            String lastName2 = p2.getLastName();
            return lastName1.compareTo(lastName2);
        }
    });

0  

You can use a TreeMap in this case where your key can be the lastname and value can be comma separated string of Firstname and ID or your value can be an ArrayList of string where you store the ID and Firstname as strings and later after retrieving convert them.

在这种情况下，您可以使用TreeMap，其中您的键可以是姓氏，值可以是逗号分隔的Firstname和ID字符串，或者您的值可以是字符串的ArrayList，其中您将ID和Firstname存储为字符串，稍后在检索转换它们之后。

The treeMap will automatically store the lastname in sorted order.

treeMap将按排序顺序自动存储姓氏。

0  

Create a Person class

创建一个Person类

public class Person implements Comparable {

   private String firstName;
   private String lastName;
   private String username;
   private String password;

  //do stuff

  public int compareTo(Person p) {
     lastName.compareTo(p.lastName);
  }

  public void writeToFile(FileWriter file) {
   //Implements
 }      

}

After, short the array of elements

之后，缩短元素数组

Collections.sort(persons);

And write the persons in order

并按顺序写下这些人

for (Person p : persons) {
   p.writeToFile(fileWriter);
}

0  

The solutions you'll get here will probably all look fairly similar. Here's mine:

你在这里得到的解决方案看起来可能都非常相似。这是我的：

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

public class User implements Comparable {
    private int id;
    private String firstName;
    private String lastName;

    public User(int id, String firstName, String lastName) {
        this.id = id;
        this.firstName = firstName;
        this.lastName = lastName;
    }

    public int compareTo(User other) {
        int lastNameComparison = lastName.compareTo(other.lastName);

        return (lastNameComparison != 0 ? lastNameComparison : firstName
                .compareTo(other.firstName));
    }

    @Override
    public String toString() {
        return String.format("%d\t%s\t%s", id, firstName, lastName);
    }

    public static void main(String... args) {
        List users = new ArrayList();
        users.add(new User(1, "John", "Smith"));
        users.add(new User(2, "Joe", "Blow"));
        users.add(new User(3, "Cat", "Dog"));

        Collections.sort(users);

        for(User user : users) {
            System.out.println(user.toString());
        }
    }
}