231105 오공완

다차원 배열

public class Main {
    public static void main(String[] args) {
        System.out.println("==일차원 배열==");
        int[] myArray = {1, 2, 3};
        System.out.println("myArray[1]= " + myArray[1]);
        for (int i = 0; i < myArray.length; i++) {
            System.out.println(myArray[i]);
        }
        for (int i : myArray) {
            System.out.println(i);
        }

        System.out.println("==이차원 배열==");
        int[][] myArray2 = {{1, 2, 3}, {4, 5, 6}};
        System.out.println("myArray2[1][2] = " + myArray2[1][2]);
        for (int i = 0; i < myArray2.length; i++) {
            for (int j = 0; j < myArray2[i].length; j++) {
                System.out.println(myArray2[i][j]);
            }
        }

        for (int[] ints : myArray2) {
            for (int anInt : ints) {
                System.out.println("anInt = " + anInt);
            }
        }
        
    }
}

컬렉션 프레임워크

import java.util.*;

public class Main{
    public static void main(String[] args) {
        //1. List
        //1-1. ArrayList
        ArrayList list1 = new ArrayList();
        list1.add(1);
        list1.add(2);
        list1.add(3);
        System.out.println("list1 = " + list1);
        list1.remove(Integer.valueOf(2));
        System.out.println("list1 = " + list1);
        list1.add(0, 10);
        System.out.println("list1 = " + list1);
        System.out.println("list1.size() = " + list1.size());
        System.out.println("list1.contains(1) = " + list1.contains(1));
        System.out.println("list1.indexOf(10) = " + list1.indexOf(10));

        //1-2. LinkedList
        System.out.println("== LinkedList ==");
        LinkedList list2 = new LinkedList();
        list2.add(1);
        list2.add(2);
        list2.add(3);
        System.out.println("list2 = " + list2);
        list2.addFirst(10);
        list2.addLast(20);
        System.out.println("list2 = " + list2);
        list2.remove(Integer.valueOf(1));
        System.out.println("list2 = " + list2);
        list2.removeFirst();
        list2.removeLast();
        System.out.println("list2 = " + list2);
        System.out.println(list2.size());
        
        //2. Set
        //2-1. HashSet
        System.out.println("== HashSet ==");
        HashSet set1 = new HashSet();
        set1.add(1);
        set1.add(2);
        set1.add(3);
        System.out.println("set1 = " + set1);
        set1.remove(1); //값으로 인식
        System.out.println("set1 = " + set1);
        set1.add(2);
        set1.add(3);
        System.out.println("set1 = " + set1); //중복처리 되어서 추가로 출력되지 않음
        System.out.println(set1.size());
        System.out.println(set1.contains(2));

        //2-2. TreeSet
        System.out.println("== TreeSet ==");
        TreeSet set2 = new TreeSet();
        set2.add(1);
        set2.add(2);
        set2.add(3);
        System.out.println("set2 = " + set2);
        set2.remove(2);
        System.out.println("set2 = " + set2);
        set2.clear();
        System.out.println("set2 = " + set2);
        set2.add(10);
        set2.add(5);
        set2.add(15);
        set2.add(15);
        System.out.println("set2 = " + set2);
        System.out.println(set2.first());
        System.out.println(set2.last());
        System.out.println(set2.lower(10));
        System.out.println(set2.higher(10));

        //3. Map
        //3-1. HashMap
        System.out.println("== HashMap ==");
        HashMap map1 = new HashMap();
        map1.put(1, "kiwi"); //키값과 데이터
        map1.put(2, "apple");
        map1.put(3, "mango");
        System.out.println("map1 = " + map1);
        map1.remove(2);
        System.out.println("map1 = " + map1);
        System.out.println("map1.get(1) = " + map1.get(1));

        //3-2. TreeMap
        System.out.println("== TreeMap ==");
        TreeMap map2 = new TreeMap();
        map2.put(10, "kiwi");
        map2.put(5, "apple");
        map2.put(15, "mango");
        System.out.println("map2 = " + map2);
        System.out.println(map2.firstEntry());
        System.out.println(map2.firstKey());
        System.out.println(map2.lastEntry());
        System.out.println(map2.lastKey());
        System.out.println(map2.lowerEntry(10));
        System.out.println(map2.higherEntry(10));

    }
}