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컬렉션프레임웍(Collections Framework) - TreeMap 본문

자바/Collections Framework

컬렉션프레임웍(Collections Framework) - TreeMap

은은하게미친자 2022. 10. 2. 22:38
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package coding;
 
 
import java.util.*;
 
 
class code1_Treemap {
    public static void main(String[] args) {
        System.out.println("TreeMap test"); 
        //이진검색형태의 키와 값이 쌍으로 이루어진 데이터형태
        //범위검색이나 정렬에 좋다!
        
        String[] arr = {"a","b","c","a","c","t","t","t","c","t","t"};
        System.out.println("배열원본");
        System.out.println(Arrays.toString(arr));
        
        TreeMap map = new TreeMap();
        
        for (int i=0; i < arr.length; i++) {
            if (map.containsKey(arr[i])) {
                Integer value = (Integer)map.get(arr[i]);
                map.put(arr[i], new Integer(value+1));
            } else {
                map.put(arr[i], new Integer(1));
            }
        }
        
        System.out.println(map);
        System.out.println("기본정렬 : 값의 종류(키), 갯수(값)");
        
        Iterator it = map.entrySet().iterator();
        while (it.hasNext()) {
            System.out.println(it.next());
        }
        
        System.out.println("값의 크기 큰순으로 정렬");
        Set set = map.entrySet();
        //set을 list로 변환
        
        List list = new ArrayList(set);
        System.out.println(list);
        //값 오름차순 정렬
        Collections.sort(list, new ValueAsce());
        System.out.println(list);
        //값 내림차순 정렬
        Collections.sort(list, new ValueDesc());
        System.out.println(list);
    }
 
    static class ValueAsce implements Comparator{
 
        @Override
        public int compare(Object o1, Object o2) {
            if (o1 instanceof Map.Entry && o2 instanceof Map.Entry) {
                Map.Entry e1 = (Map.Entry)o1;
                Map.Entry e2 = (Map.Entry)o2;                
                
                int v1 = ((Integer)e1.getValue()).intValue();
                int v2 = ((Integer)e2.getValue()).intValue();
                //오름차순은     같으면0 크면-1 작으면 1, 
                //내림차순은     같으면0 크면1  작으면 -1, 
                return v1-v2;
            }
            
            return -1;
        }
    }
    static class ValueDesc implements Comparator{
        
        @Override
        public int compare(Object o1, Object o2) {
            if (o1 instanceof Map.Entry && o2 instanceof Map.Entry) {
                Map.Entry e1 = (Map.Entry)o1;
                Map.Entry e2 = (Map.Entry)o2;                
                
                int v1 = ((Integer)e1.getValue()).intValue();
                int v2 = ((Integer)e2.getValue()).intValue();
                //오름차순은     같으면0 크면-1 작으면 1, 
                //내림차순은     같으면0 크면1  작으면 -1, 
                return v2-v1;
            }
            
            return -1;
        }
    }
}
 
 
 
 
 
 
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