How to sort an ArrayList in Java [duplicate]

问题:

This question already has an answer here:

• Sort ArrayList of custom Objects by property 25 answers

I have a class named Fruit. I am creating a list of this class and adding each fruit in the list. I want to sort this list based on the order of fruit name.

public class Fruit{

    private String fruitName;
    private String fruitDesc;
    private int quantity;

    public String getFruitName() {
        return fruitName;
    }
    public void setFruitName(String fruitName) {
        this.fruitName = fruitName;
    }
    public String getFruitDesc() {
        return fruitDesc;
    }
    public void setFruitDesc(String fruitDesc) {
        this.fruitDesc = fruitDesc;
    }
    public int getQuantity() {
        return quantity;
    }
    public void setQuantity(int quantity) {
        this.quantity = quantity;
    }
}

and I am creating its list using for loop

List<Fruit>  fruits= new ArrayList<Fruit>();

Fruit fruit;
for(int i=0;i<100;i++)
{
   fruit = new fruit();
   fruit.setname(...);
   fruits.add(fruit);
}

and I need to sort this arrayList using the fruit name of each object in the list

how??

回答1:

Use a Comparator like this:

List<Fruit> fruits= new ArrayList<Fruit>();

Fruit fruit;
for(int i = 0; i < 100; i++)
{
  fruit = new Fruit();
  fruit.setname(...);
  fruits.add(fruit);
}

// Sorting
Collections.sort(fruits, new Comparator<Fruit>() {
        @Override
        public int compare(Fruit fruit2, Fruit fruit1)
        {

            return  fruit1.fruitName.compareTo(fruit2.fruitName);
        }
    });

Now your fruits list is sorted based on fruitName.

回答2:

Implement Comparable interface to Fruit.

public class Fruit implements Comparable<Fruit> {

It implements the method

@Override
    public int compareTo(Fruit fruit) {
        //write code here for compare name
    }

Then do call sort method

Collections.sort(fruitList);

回答3:

Try BeanComparator

BeanComparator fieldComparator = new BeanComparator(
                \"fruitName\");
Collections.sort(fruits, fieldComparator);