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Java Sort ArrayList

Submitted by Deepthi on Sat, 11/13/2010 - 18:50

This Java Sort ArrayList example shows how to Sort an ArrayList in Java.

import java.util.ArrayList;
import java.util.Collections;
 
//Java Sort ArrayList
 
public class JavaSortArrayList {
    
    public static void main(String args){
       
        //create new ArrayList
        ArrayList<Integer> aListNumbers = new ArrayList<Integer>();
        aListNumbers.add(23);
        aListNumbers.add(11);
        aListNumbers.add(43);
        aListNumbers.add(46);
        aListNumbers.add(98);
        aListNumbers.add(7);
        aListNumbers.add(86);
       
        System.out.println("ArrayList before sort " + aListNumbers);
        /*
         * To sort ArrayList use,
         * Collections.sort(List list) method.
         */
       
        Collections.sort(aListNumbers);
        System.out.println("ArrayList after sort" + aListNumbers);
       
        /*
         * Note: All elements in the ArrayList must implement Comparable interface
         * in order for sort to work. Additionally, none of the elements should throw
         * ClassCastException while being compared with each other.
         *
         * In above example, ArrayList contains all Integer elements, so sort will work
         * by default. If we have an ArrayList which contains objects of custom class,
         * then that class must implement Comparable interface for the sort to work.
         *
         * See the example below.
         */
 
        //create new ArrayList with custom objects of Class Car.
        ArrayList<Car> aListCars = new ArrayList<Car>();
        aListCars.add(new Car("Merc Benz", 3000000));
        aListCars.add(new Car("Maruti Suzuki 800", 280000));
        aListCars.add(new Car("Honda City", 950000));
        aListCars.add(new Car("Tata Nano", 180000));
       
        System.out.println("ArrayList before sort " + aListCars);
 
        //sort ArrayList of Car objects
        Collections.sort(aListCars);
       
        System.out.println("ArrayList after sort " + aListCars);
       
    }
}
 
class Car implements Comparable{
    
    private String name;
    private int price;
    
    public Car(String name, int price){
        this.name = name;
        this.price = price;
    }
    
    public String getName(){
        return this.name;
    }
    
    public int getPrice(){
        return this.price;
    }
    
    //this method must be defined if we are implementing Comparable interface
    public int compareTo(Object otherCar){
       
        if(otherCar instanceof Car){
            throw new ClassCastException("Not a valid Car object!!");
        }
       
        Car tempCar = (Car)otherCar;
       
        if(this.getPrice() > tempCar.getPrice()){
            return 1;
        }else if(this.getPrice() < tempCar.getPrice()){
            return -1;
        }else{
            return 0;
        }
    }
}

Deepthi's blog

Dear your sol is the best

Submitted by Anonymous on Thu, 12/16/2010 - 11:01.

Dear your sol is the best sol....thanks ...

Excuse me. I have 2 questions

Submitted by Anonymous on Mon, 01/10/2011 - 07:22.

Excuse me. I have 2 questions for you. 1.Is that a big deal by using a built-in method sort and writing sort program ? 2.If i have too many employees how would i write too many if-else conditions ?