java 객체 정렬

• 첫 번째 방법

import java.util.ArrayList;
import java.util.Collections;

public class Main {
	
	static class Obj implements Comparable<Obj>{
		String s;
		int n;
		
		public Obj(String s, int n) {
			this.s = s;
			this.n = n;
		}
		
		@Override
		public int compareTo(Obj o) {
			
			return Integer.compare(this.n, o.n); // n 오름차순 정렬
//			return this.s.compareTo(o.s); // s 오름차순 정렬
		}
	}
	
	public static void main(String[] args) {
		
		ArrayList<Obj> list = new ArrayList();
		
		list.add(new Obj("B", 3));
		list.add(new Obj("E", 5));
		list.add(new Obj("G", 1));
		list.add(new Obj("A", 8));
		list.add(new Obj("D", 10));
		list.add(new Obj("Z", 7));
		list.add(new Obj("X", 6));
		
		Collections.sort(list);
		
		for(Obj o : list) {
			System.out.println(o.s + " " + o.n);
		}
	}
}

 

• 두 번째 방법

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;

public class Main {
	
	static class Obj {
		String s;
		int n;
		public Obj(String s, int n) {
			this.s = s;
			this.n = n;
		}
		
	}
	
	public static void main(String[] args) {
		ArrayList<Obj> list = new ArrayList();
		
		list.add(new Obj("B", 3));
		list.add(new Obj("E", 5));
		list.add(new Obj("G", 1));
		list.add(new Obj("A", 8));
		list.add(new Obj("D", 10));
		list.add(new Obj("Z", 7));
		list.add(new Obj("X", 6));
		
		Collections.sort(list, new Comparator<Obj>() {
			public int compare(Obj o1, Obj o2) {
//				return o1.s.compareTo(o2.s);
				return Integer.compare(o1.n, o2.n);
			}
		});
		
		for(Obj o : list) {
			System.out.println(o.s + " " + o.n);
		}
	}
}