如何在 Java 中使用可比接口对 TreeSet 元素进行排序？

原文:https://www . geeksforgeeks . org/如何使用 java 中的可比接口对 treeset 元素进行排序/

TreeSet 是 Java 中 SortedSet 接口的一个实现，使用一个 Tree 进行存储。无论是否提供明确的比较器，元件的顺序都由设置使用它们的自然顺序来维护。

要使用 java 中的可比接口对 TreeSet 元素进行排序，首先，我们创建一个实现可比接口的类 Student。在这个类中，我们覆盖了 compareTo() 方法。

*伪码:*

// Student class implements comparable interface

class Student implements Comparable<Student> {
    Integer marks;

    Student(Integer marks) {
        this.marks = marks;
    }

    // override toString method
    public String toString() {
        return (" " + this.marks);
    }

    // Override compareTo method to sort LinkedHashSet in ascending order
    public int compareTo(Student stu) {
        return this.marks.compareTo(stu.marks);
    }
}

*以下是上述方法的实现:*

*例 1:*

Java 语言(一种计算机语言，尤用于创建网站)

// Java program to demonstrate how to Sort TreeSet using
// Comparable interface in ascending order

import java.util.*;

// Student class implements comparable interface
class Student implements Comparable<Student> {

    Integer marks;

    Student(Integer marks) { this.marks = marks; }

    // override toString method
    public String toString() { return (" " + this.marks); }

    // Override compareTo method to sort TreeSet in
    // ascending order
    public int compareTo(Student stu)
    {
        return this.marks.compareTo(stu.marks);
    }
}

class GFG {
    public static void main(String[] args)
    {

        // New TreeSet
        TreeSet<Student> set = new TreeSet<>();

        // Adding elements to the set
        set.add(new Student(500));
        set.add(new Student(300));
        set.add(new Student(400));
        set.add(new Student(100));
        set.add(new Student(200));

        // Print TreeSet sorted in ascending order
        System.out.println("Sort elements in ascending order : " + set);

    }
}

**Output

Sort elements in ascending order : [ 100,  200,  300,  400,  500]
```** 

****例 2:****

## **Java 语言(一种计算机语言，尤用于创建网站)**

```java
// Java program demonstrate how to Sort TreeSet using
// Comparable interface in descending order

import java.util.*;

// Student class implements comparable interface
class Student implements Comparable<Student> {

    Integer marks;

    Student(Integer marks) { this.marks = marks; }

    // override toString method
    public String toString() { return (" " + this.marks); }

    // Override compareTo method to sort TreeSet in
    // descending order
    public int compareTo(Student stu)
    {
        return stu.marks.compareTo(this.marks);
    }
}

class GFG {
    public static void main(String[] args)
    {

        // New TreeSet
        TreeSet<Student> set = new TreeSet<>();

        // Adding elements to the set
        set.add(new Student(500));
        set.add(new Student(300));
        set.add(new Student(400));
        set.add(new Student(100));
        set.add(new Student(200));

        // Print TreeSet sorted in descending order
        System.out.println("Sort elements in descending order : " + set);

    }
}

**Output

java Sort elements in descending order : [ 500, 400, 300, 200, 100]**

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