[Java] ArrayList 오름차순, 내림차순 Example

 

ArrayList 오름차순 정렬 

방법 1

import java.util.ArrayList;
import java.util.Collections;
 
public class Ascending_Sort {
    public static void main(String[] args) {
 
        ArrayList<Integer> data = new ArrayList<Integer>();
 
        /* 임의로 데이터 삽입 */
        data.add(3);
        data.add(7);
        data.add(5);
 
        /* Default Ascending Sort */
        Collections.sort(data); 
 
        output(data);
    }
 
    private static void output(ArrayList<Integer> data) {
        int size = data.size();
        for (int i = 0; i < size; i++) {
            System.out.print(data.get(i) + " ");
        }
        System.out.println();
    }
}

 

방법 2

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
 
public class Ascending_Sort {
    public static void main(String[] args) {
 
        ArrayList<Integer> data = new ArrayList<Integer>();
 
        /* 임의로 데이터 삽입 */
        data.add(3);
        data.add(7);
        data.add(5);
 
        Ascending ascending = new Ascending();
        Collections.sort(data, ascending);
 
        output(data);
    }
 
    private static void output(ArrayList<Integer> data) {
        int size = data.size();
        for (int i = 0; i < size; i++) {
            System.out.print(data.get(i) + " ");
        }
        System.out.println();
    }
}
 
/* 오름차순 정렬 */
class Ascending implements Comparator<Integer> {
 
    @Override
    public int compare(Integer a, Integer b) {
        return a.compareTo(b);
    }
}

 

ArrayList 내림차순 정렬

 

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
 
public class Descending_Sort {
    public static void main(String[] args) {
 
        ArrayList<Integer> data = new ArrayList<Integer>();
 
        /* 임의로 데이터 삽입 */
        data.add(3);
        data.add(7);
        data.add(5);
 
        Descending descending = new Descending();
        Collections.sort(data, descending);
 
        output(data);
    }
 
    private static void output(ArrayList<Integer> data) {
        int size = data.size();
        for (int i = 0; i < size; i++) {
            System.out.print(data.get(i) + " ");
        }
        System.out.println();
    }
}
 
/* 내림차순 정렬 */
class Descending implements Comparator<Integer> {
 
    @Override
    public int compare(Integer a, Integer b) {
        return b.compareTo(a);
    }
}