按字母顺序排列对象的ArrayList

Question

I have to create a method that sorts an ArrayList of objects alphabetically according to email and then prints the sorted array. The part that I am having trouble with it sorting it. I have researched it and tried using Collections.sort(vehiclearray); but that didn't work for me. I was that I needed something called a comparator but couldn't figure out how it worked. Will I have to use those or can something like bubble sort or insertion sort work for this kind of thing?

This is the code that I have so far:

public static void printallsort(ArrayList<vehicle> vehiclearray){

   ArrayList<vehicle> vehiclearraysort = new ArrayList<vehicle>();
   vehiclearraysort.addAll(vehiclearray);

 //Sort
   for(int i = 0; i < vehiclearraysort.size(); i++) 
   if ( vehiclearray.get(i).getEmail() > vehiclearray.get(i+1).getEmail())

//Printing 
   for(i = 0; i < vehiclearraysort.size(); i++)           
   System.out.println( vehiclearraysort.get(i).toString() + "\n");

}

Answer 1

The sorting part can be done by implementing a custom Comparator<Vehicle> .

Collections.sort(vehiclearray, new Comparator<Vehicle>() {
    public int compare(Vehicle v1, Vehicle v2) {
        return v1.getEmail().compareTo(v2.getEmail());
    }
});

This anonymous class will be used for sorting the Vehicle objects in the ArrayList on the base of their corresponding emails alphabetically.

Upgrading to Java8 will let you also implement this in a less verbose manner with a method reference:

Collections.sort(vehiclearray, Comparator.comparing(Vehicle::getEmail));

Answer 2

Although the question already has an accepted answer I would like to share some Java 8 solution

// if you only want to sort the list of Vehicles on their email address
Collections.sort(list, (p1, p2) -> p1.getEmail().compareTo(p2.getEmail()));

.

// sort the Vehicles in a Stream
list.stream().sorted((p1, p2) -> p1.getEmail().compareTo(p2.getEmail()));

.

// sort and print with a Stream in one go
list.stream().sorted((p1, p2) -> p1.getEmail().compareTo(p2.getEmail())).forEach(p -> System.out.printf("%s%n", p));

.

// sort with an Comparator (thanks @Philipp)
// for the list
Collections.sort(list, Comparator.comparing(Vehicle::getEmail));
// for the Stream
list.stream().sorted(Comparator.comparing(Vehicle::getEmail)).forEach(p -> System.out.printf("%s%n", p));

Answer 3

In this link you can find code which will help you to sort arraylist of objects in descending and ascending order.

http://beginnersbook.com/2013/12/java-arraylist-of-object-sort-example-comparable-and-comparator/

Answer 4

package srikanthdukuntla;

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

public class AlphabetsOrder {

public static void main(String[] args) {

    String temp;
    List<String> str= new ArrayList<String>();

    str.add("Apple");
    str.add("zebra");
    str.add("Umberalla");
    str.add("banana");
    str.add("oxo");
    str.add("dakuntla");
    str.add("srikanthdukuntla");
    str.add("Dukuntla");

    for(int i=0;i<str.size();i++){

        for(int j=i+1;j<str.size();j++){

     if(str.get(i).compareTo(str.get(j))<0){

            temp=str.get(i);
            str.set(i, str.get(j));
            str.set(j,temp );   

     }
        }
    }

  System.out.println("List of words in alphabetical order   "+str);

}

}

Answer 5

最明显

vehiclearray.sort(Comparator.comparing(Vehicle::getEmail()));