6. 자료구조와 컬렉션프레임워크

ArrayList<String> list = new ArrayList<>();     // 권장안됨
List<String> list = new ArrayList<>();  // 권장됨

Collection<String> c1 = new HashSet<>();
Collection<String> c2 = Arrays.asList("three", "four"); 
Collection<String> c3 = Collections.singleton("five");

c1.add("one");
c1.addAll(c2);

c1.remove("one");
c1.remove("c2");
c1.retainAll("four");
c1.clear();

c1.isEmpty();
c1.contains("zero");
c1.containsAll(c2);

int size = c1.size();
Object[] converted1 = c1.toArray();
String[] converted2 = c1.toArray(new String[c1.size()]);

for(String s : c1) {
    System.out.println(s);			
}

String[] converted2 = c1.toArray(new String[c1.size()]);
for(int i=0; i < converted2.length; i++) {
    System.out.println(converted2[i]);
}

Iterator iter = c1.iterator();
while(iter.hasNext()) {
    System.out.println(iter.next());
}

c1.forEach(s -> System.out.println(s));
c1.forEach(System.out::println);

public class CollectionTest {
    public static void main(String[] args) {
        // Create a new HashSet and add data
        Collection<String> c1 = new HashSet<>();
        c1.add("one");
        c1.add("two");

        // Create a new List with two values
        Collection<String> c2 = Arrays.asList("three", "four");
        Collection<String> c3 = Collections.singleton("five");

        // add all data in c2, c3 to c1
        c1.addAll(c2);
        c1.addAll(c3);

        // get size of collection
        System.out.println("Size of c1 : " + c1.size());

        // convert collection to array
        Object[] converted1 = c1.toArray();
        String[] converted2 = c1.toArray(new String[c1.size()]);

        // print all data in collection using for loop
        for (String s : c1) {
            System.out.println(s);
        }

        // access and print all data in the array which converted from collection
        for (int i = 0; i < converted2.length; i++) {
            System.out.println(converted2[i]);
        }

        // get Iterator object from collection and access the data
        Iterator iter = c1.iterator();
        while (iter.hasNext()) {
            System.out.println(iter.next());
        }

        // run specific code using every elements in the collection
        c1.forEach(System.out::println);
    }
}

List<String> l1 = new ArrayList<>();
List<String> l2 = Arrays.asList("one", "two"); 
List<String> l3 = List.of("three", "four");

l1.add("five");
l1.allAll(l2);
l1.set(0,"zero");

System.out.println(l1.get(0));

LinkedList<String> llist = new LinkedList<>();
llist.addAll(l2);
llist.addAll(1,l3);
llist.add("five");

Collections.sort(l1);
System.out.println(l1);

l1.sort(new Comparator<Object>() {
    @Override
    public int compare(Object o1, Object o2) {
        return o2.toString().compareTo(o1.toString());
    }
});

l1.stream().sorted((o1, o2) -> o2.toString().compareTo(o1.toString())).forEach(System.out::println);

public class ListTest {
    public static void main(String[] args) {
        // create new List
        List<String> l1 = new ArrayList<>();
        List<String> l2 = Arrays.asList("one", "two");
        List<String> l3 = List.of("three", "four");

        // add data to List
        l1.addAll(l2);
        l1.addAll(1, l3);
        l1.add("five");

        System.out.println("## element in List");
        System.out.println(l1);

        // create new LinkedList and add data
        LinkedList<String> llist = new LinkedList<>();
        llist.addAll(l2);
        llist.addAll(1, l3);
        llist.add("five");

        System.out.println("## element in LinkedList");
        System.out.println(l1);

        // access data with index
        System.out.println("## first element: " + l1.get(0));
        System.out.println("## last index of three: " + l1.lastIndexOf("three"));

        // change data in List
        l1.set(0, "zero");
        System.out.println("## after set(): element in LinkedList");
        System.out.println(l1);

        // Descending sort
        Collections.sort(l1);
        System.out.println("## Descending sort of l1");
        System.out.println(l1);

        // Ascending sort
        l1.sort(new Comparator<Object>() {
            @Override
            public int compare(Object o1, Object o2) {
                return o2.toString().compareTo(o1.toString());
            }

        });
        System.out.println("## Ascending sort of l1");
        System.out.println(l1);

        // Ascending sort with stream api
        System.out.println("## Ascending sort with stream api");
        l1.stream().sorted((o1, o2) -> o2.toString().compareTo(o1.toString())).forEach(System.out::println);
    }
}

Set<String> s1 = new HashSet<>();
Set<String> s2 = Set.of("three","four");

s1.addAll(Arrays.asList("one","two"));
s1.addAll(s2);
s1.add("five");
s1.add("two"); // 기존에 있으므로 새로 추가 안됨
s1.remove("five");
boolean check = s1.contains("one");

LinkedHashSet<String> lset = new LinkedHashSet<>();
lset.addAll(Arrays.asList("one","two","three","four"));
lset.add("five");

Iterator<String> iter = lset.iterator();
while(iter.hasNext()) {
    System.out.println(iter.next());
}

Set<Integer> tset = new TreeSet<>();
tset.addAll(Arrays.asList(50,10,60,20));

tset.stream().sorted((o1, o2) -> o2.toString().compareTo(o1.toString())).forEach(System.out::println);

public class SetTest {
    public static void main(String[] args) {
        // create new Set
        Set<String> s1 = new HashSet<>();
        Set<String> s2 = Set.of("three", "four");

        // add element to Set
        s1.addAll(Arrays.asList("one", "two"));
        s1.addAll(s2);
        s1.add("five");
        s1.add("two");
        s1.remove("five");

        System.out.println("## element in Set");
        System.out.println(s1);

        // print all elements using stream api
        s1.stream().forEach(System.out::println);

        System.out.println("## check exist element in Set");
        System.out.println(s1.contains("one"));

        // create new LinkedHashSet and add elements
        Set<String> lset = new LinkedHashSet<>();
        lset.addAll(Arrays.asList("one", "two", "three", "four"));
        lset.add("five");

        System.out.println("\n## element in LinkedHashSet");
        System.out.println(lset);

        // get Iterator from LinkedHashSet
        System.out.println("## print element using Iterator");
        Iterator<String> iter = lset.iterator();
        while (iter.hasNext()) {
            System.out.println(iter.next());
        }

        // create new TreeSet and add elements
        Set<Integer> tset = new TreeSet<>();
        tset.addAll(Arrays.asList(50, 10, 60, 20));

        System.out.println("\n## elements in TreeSet");
        System.out.println(tset);

        // Descending sort with stream api
        System.out.println("## Descending sort with stream api");
        tset.stream().sorted((o1, o2) -> o2.toString().compareTo(o1.toString())).forEach(System.out::println);
    }
}

Map<String,String> map = new HashMap<>();
map.put("109875","홍길동");
map.put("109894","김사랑");
System.out.println(map.get("109894")); // 김사랑

public class MapTest {

    public static void main(String[] args) {
        Map<String, String> map = new HashMap<>();
        map.put("1922876", "Apple Iphone");
        map.put("1922877", "Apple Ipad");
        map.put("2136861", "Samsung Galaxy");
        map.put("2136863", "Samsung Tablet");

        System.out.println("1922877: " + map.get("1922877"));

        System.out.println("--------------------");
        for (Map.Entry<String, String> entry : map.entrySet()) {
            System.out.printf("%s:%s\n", entry.getKey(), entry.getValue());
        }

        System.out.println("--------------------");
        for (String s : map.keySet()) {
            System.out.printf("%s\n", s);
        }

        System.out.println("--------------------");
        for (String s : map.values()) {
            System.out.printf("%s\n", s);
        }
    }
}

public class MapListTest {
    public static void main(String[] args) {
        List<Integer> s1 = Arrays.asList(95, 89, 93, 87, 94);
        List<Integer> s2 = Arrays.asList(99, 79, 91, 89, 91);
        List<Integer> s3 = Arrays.asList(93, 81, 95, 88, 99);

        Map<String, List<Integer>> student = new HashMap<>();
        student.put("홍길동", s1);
        student.put("김사랑", s2);
        student.put("아무개", s3);

        Scanner scan = new Scanner(System.in);
        System.out.print("## 성적 조회할 이름을 입력하세요: ");
        String input = scan.next();

        int total = 0;
        for (int s : student.get(input)) {
            total += s;
        }

        System.out.printf("총점: %d, 평균: %d", total, total / 5);
    }
}