컬렉션 프레임워크

Java 프로그래밍 - 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() = " + 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);
        System.out.println("set1 = " + set1);
        set1.add(2);
        set1.add(3);
        System.out.println("set1 = " + set1);
        System.out.println("set1.size() = " + set1.size());
        System.out.println("set1.contains(2) = " + 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() = " + set2.first());
        System.out.println("set2.last() = " + set2.last());
        System.out.println("set2.lower(10) = " + set2.lower(10));
        System.out.println("set2.higher(10) = " + set2.higher(10));


//      3. Map
//      3-1. HashMap
        System.out.println("== HashMap ==");
        HashMap map1 = new HashMap();
        map1.put(1, "kiwi");
        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() = " + map2.firstEntry());
        System.out.println("map2.firstKey() = " + map2.firstKey());
        System.out.println("map2.lastEntry() = " + map2.lastEntry());
        System.out.println("map2.lastKey() = " + map2.lastKey());
        System.out.println("map2.lowerEntry(10) = " + map2.lowerEntry(10));
        System.out.println("map2.higherEntry(10) = " + map2.higherEntry(10));

    }
}

list1 = [1, 2, 3]
list1 = [1, 3]
list1 = [10, 1, 3]
list1.size() = 3
list1.contains(1) = true
list1.indexOf(10) = 0
== LinkedList ==
list2 = [1, 2, 3]
list2 = [10, 1, 2, 3, 20]
list2 = [10, 2, 3, 20]
list2 = [2, 3]
list2.size() = 2
== HashSet ==
set1 = [1, 2, 3]
set1 = [2, 3]
set1 = [2, 3]
set1.size() = 2
set1.contains(2) = true
== TreeSet ==
set2 = [1, 2, 3]
set2 = [1, 3]
set2 = []
set2 = [5, 10, 15]
set2.first() = 5
set2.last() = 15
set2.lower(10) = 5
set2.higher(10) = 15
== HashMap ==
map1 = {1=kiwi, 2=apple, 3=mango}
map1 = {1=kiwi, 3=mango}
map1.get(1) = kiwi
== TreeMap ==
map2 = {5=apple, 10=kiwi, 15=mango}
map2.firstEntry() = 5=apple
map2.firstKey() = 5
map2.lastEntry() = 15=mango
map2.lastKey() = 15
map2.lowerEntry(10) = 5=apple
map2.higherEntry(10) = 15=mango

로또 번호 만들기

// Practice
// 로또 번호 만들기

import java.util.*;

public class Practice {
    public static void main(String[] args) {

        HashSet set = new HashSet();

        for (int i = 0; set.size() < 6; i++) {
            int num = (int)(Math.random() * 45) + 1;
            set.add(num);
        }

        LinkedList list = new LinkedList(set);
        Collections.sort(list);
        System.out.println("로또 번호: " + list);
    }
}

로또 번호: [1, 8, 17, 32, 35, 41]
로또 번호: [13, 15, 21, 34, 37, 39]
로또 번호: [10, 14, 20, 33, 42, 45]