「java入門」 Collections.sort()で List

2017年9月20日

Javaコード:
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class ListSort {

public static void main(String[] args) {

List<Map<Object, Object>> list = new ArrayList<Map<Object, Object>>();

Map<Object, Object> map = new HashMap<Object, Object>();

Map<Object, Object> map1 = new HashMap<Object, Object>();
Map<Object, Object> map2 = new HashMap<Object, Object>();
Map<Object, Object> map3 = new HashMap<Object, Object>();

map.put(“number", “1.46");
map1.put(“number", “2");
map2.put(“number", “1.89");
map3.put(“number", “1.68");
list.add(map);
list.add(map1);
list.add(map2);
list.add(map3);

Collections.sort(list, new Comparator<Map<Object, Object>>() {

public int compare(Map<Object, Object> o1, Map<Object, Object> o2) {

int mapval1 = (int)Double.parseDouble((String) o1.get(“number"))*100 ;
int mapval2 = (int)Double.parseDouble((String) o2.get(“number"))*100;
return mapval1 – mapval2;
}
});
System.out.println(list);
}