如何使用Java中的可比较接口对 LinkedHashSet 元素进行排序？

LinkedHashSet 是 HashSet 的有序版本，它在所有元素之间维护一个双向链表。当需要维护迭代顺序时，使用这个类。当遍历 HashSet 时，顺序是不可预测的，而 LinkedHashSet 允许我们按照元素插入的顺序遍历元素。

为了首先在Java中使用 Comparable 接口对 LinkedHashSet 元素进行排序，我们创建了一个实现 Comparable 接口的 Student 类。在这个类中，我们覆盖了 compareTo() 方法。

// Student class implements comparable interface

class Student implements Comparable {
    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);
    }
}

然后我们将集合传递给 TreeSet 构造函数以对元素进行排序。

// TreeSet to sort LinkedHashSet using comparable
TreeSet tree_set = new TreeSet<>(set);

示例 1

Java

// Java program demonstrate how to Sort LinkedHashSet using
// Comparable interface
import java.util.*;
 
// Student class implements comparable interface
class Student implements Comparable {
    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);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New LinkedHashSet
        LinkedHashSet set = new LinkedHashSet<>();
 
        // 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 Before sort
        System.out.println(
            "Before sort elements in ascending order : "
            + set);
 
        // TreeSet to sort LinkedHashSet using comparable
        TreeSet tree_set = new TreeSet<>(set);
 
        // Print after sorting
        System.out.println(
            "After sort elements in ascending order : "
            + tree_set);
    }
}

输出

Before sort elements in ascending order : [ 500,  300,  400,  100,  200]
After sort elements in ascending order : [ 100,  200,  300,  400,  500]

示例 2

Java

// Java program demonstrate how to Sort LinkedHashSet using
// Comparable interface
import java.util.*;
 
// Student class implements comparable interface
class Student implements Comparable {
    Integer marks;
 
    Student(Integer marks) { this.marks = marks; }
 
    // override toString method
    public String toString() { return (" " + this.marks); }
 
    // Override compareTo method to sort LinkedHashSet in
    // descending order
    public int compareTo(Student stu)
    {
        return stu.marks.compareTo(this.marks);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New LinkedHashSet
        LinkedHashSet set = new LinkedHashSet<>();
 
        // 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 Before sort
        System.out.println(
            "Before sort elements in descending order : "
            + set);
 
        // TreeSet to sort LinkedHashSet using comparable
        TreeSet tree_set = new TreeSet<>(set);
 
        // Print after sorting
        System.out.println(
            "After sort elements in descending order : "
            + tree_set);
    }
}

输出：

Before sort elements in descending order : [ 500,  300,  400,  100,  200]
After sort elements in descending order : [ 500,  400,  300,  200,  100]