Ordenar LinkedHashMap por claves usando una interfaz comparable en Java

LinkedHashMap es como HashMap con una característica adicional de mantener un orden de elementos insertados en él. HashMap nunca mantuvo la pista y el orden de inserción que proporciona LinkedHashMap donde se puede acceder a los elementos en su orden de inserción. 

Para ordenar LinkedHashMap por claves usando la interfaz comparable en Java primero, creamos una clase que implementa la interfaz comparable. En esta clase, anulamos el método compareTo() .

// Student class implements comparable interface

class Student implements Comparable<Student> {
    String name;

    Student(String name) {
        this.name = name;
    }

    // Override toString method
    public String toString() {
        return this.name;
    }

    // Override compareTo method
    public int compareTo(Student stu) {
        return this.name.compareTo(stu.name);
    }
}

Y luego pasamos el LinkedHashMap al constructor TreeMap para ordenar.

TreeMap<Student, Integer> tree_map = new TreeMap<>(map);

A continuación se muestra la implementación completa del enfoque:

Ejemplo 1

// Java program demonstrate how to Sort LinkedHashMap by
// keys using Comparable interface
import java.util.*;
 
// Student class implements comparable interface
class Student implements Comparable<Student> {
    String name;
 
    Student(String name) { this.name = name; }
 
    // override toString method
    public String toString() { return this.name; }
 
    // Override compareTo method to sort LinkedHashMap keys
    // in ascending order
    public int compareTo(Student stu)
    {
        return this.name.compareTo(stu.name);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New LinkedHashMap
        LinkedHashMap<Student, Integer> map
            = new LinkedHashMap<>();
 
        // Adding elements to the map
        map.put(new Student("Bina"), 200);
        map.put(new Student("Akshay"), 400);
        map.put(new Student("Chintu"), 500);
 
        // Print Before sort
        System.out.println(
            "Before sort keys in ascending order : " + map);
 
        // TreeMap to sort LinkedHashMap using comparable
        TreeMap<Student, Integer> tree_map
            = new TreeMap<>(map);
 
        // Print after sorting
        System.out.println(
            "After sort keys in ascending order : "
            + tree_map);
    }
}

Before sort keys in ascending order : {Bina=200, Akshay=400, Chintu=500}
After sort keys in ascending order : {Akshay=400, Bina=200, Chintu=500}

Ejemplo 2

// Java program demonstrate how to Sort LinkedHashMap by
// keys using Comparable interface
import java.util.*;
 
// Student class implements comparable interface
class Student implements Comparable<Student> {
    String name;
 
    Student(String name) { this.name = name; }
 
    // override toString method
    public String toString() { return this.name; }
 
    // Override compareTo method to sort LinkedHashMap keys
    // in descending order
    public int compareTo(Student stu)
    {
        return stu.name.compareTo(this.name);
    }
}
 
class GFG {
    public static void main(String[] args)
    {
 
        // New LinkedHashMap
        LinkedHashMap<Student, Integer> map
            = new LinkedHashMap<>();
 
        // Adding elements to the map
        map.put(new Student("Bina"), 200);
        map.put(new Student("Akshay"), 400);
        map.put(new Student("Chintu"), 500);
 
        // Print Before sort
        System.out.println(
            "Before sort keys in descending order : " + map);
 
        // TreeMap to sort LinkedHashMap using comparable
        TreeMap<Student, Integer> tree_map
            = new TreeMap<>(map);
 
        // Print after sorting
        System.out.println(
            "After sort keys in descending order : "
            + tree_map);
    }
}

Before sort keys in descending order : {Bina=200, Akshay=400, Chintu=500}
After sort keys in descending order : {Chintu=500, Bina=200, Akshay=400}