컬렉션 예시들

1. Thread - Vector, HashTable, HashMap

 

Vector  

package Collection;

import java.util.List;
import java.util.Vector;

public class Vector1 {

    public static void main (String[] args){

        List<Board> list = new Vector<>();
        Thread th1 = new Thread(new BoardTask(list));
        Thread th2 = new Thread(new BoardTask2(list));

        th1.start();
        th2.start();

        try{
            th1.join();
            th2.join();
        }catch (Exception e){}


        int size = list.size();
        System.out.println("총 객체 수:" +size);
        System.out.println();
    }

}

class Board {
    String title;
    String content;
    String Auth;

    Board(String title, String content, String Auth){
        this.title = title;
        this.content = content;
        this.Auth = Auth;
    }
}

class BoardTask implements Runnable{
    private List<Board> list;
    BoardTask(List<Board> list){
        this.list = list;
    }
    @Override
    public void run() {
        if(this.list != null)
            for(int i=1; i<=1000;i++)
                list.add(new Board("제목"+i,"내용"+i,"글쓴이"+i));
    }
}

class BoardTask2 implements Runnable{
    private List<Board> list;
    BoardTask2(List<Board> list){
        this.list = list;
    }
    @Override
    public void run() {
        if(this.list != null)
            for(int i=1001; i<=2000;i++)
                list.add(new Board("제목"+i,"내용"+i,"글쓴이"+i));
    }
}

 

HashTable

public class HashTable1 {
    public static void main(String[] args){

        Map<String, Integer> map = new Hashtable<>();

        Thread threadA = new Thread(){
            @Override
            public void run(){
              for(int i=1; i<=1000;i++)
                  map.put(String.valueOf(i),i);
            }
        };

        Thread threadB = new Thread(){
            @Override
            public void run(){
                for(int i=1001; i<=2000;i++)
                    map.put(String.valueOf(i),i);
            }
        };

        threadA.start();
        threadB.start();

        try{
            threadA.join();
            threadB.join();
        }catch (Exception e){}

        int size = map.size();
        System.out.println("총 엔트리 수:"+size);
        System.out.println();

    }

}

 

 

 

 

2. Hash set

public class HashSet1 {
    public static void main(String[] args){

        Set<String> set = new HashSet<>();

        set.add("Java");
        set.add("JDBC");
        set.add("JSP");
        set.add("Java");
        set.add("Spring");

        int size = set.size();
        System.out.println(size);
    }

}

 

3 Hashmap

public class HashMapEx {

    public static void main(String[] args){

        Map<String,Integer> map = new HashMap<>();

        //객체 저장
        map.put("신용권",85);
        map.put("홍길동",95);
        map.put("동장군",87);
        map.put("홍길동",85);

        //키로 값 얻기
        String key = "홍길동";
        int value = map.get(key);
        System.out.println(key +" : "+value);
        System.out.println();

        //키 Set 컬렉션 얻고, 키와 값 얻기
        Set<String> keySet = map.keySet();
        Iterator<String> keyIterator = keySet.iterator();

        while(keyIterator.hasNext()){
          String k = keyIterator.next();
          Integer v = map.get(k);
          System.out.println(k + ":" + v);
        }
        System.out.println();

        //엔트리 set 컬렉션을 얻고, 반복헤서 키와 값 얻기

        Set<Map.Entry<String,Integer>> entrySet = map.entrySet();
        Iterator<Map.Entry<String,Integer>> entryIterator = entrySet.iterator();
        while (entryIterator.hasNext()){
            Map.Entry<String,Integer> ent= entryIterator.next();
            String k = ent.getKey();
            Integer v = ent.getValue();
            System.out.println(k + " : "+ v);
        }
        System.out.println();

        //키로 엔트리 삭제
        map.remove("홍길동");
        System.out.println("총 Entey 수:" + map.size());
        System.out.println();
        

    }

}

 

4 properties

public class PropertiesEx {
    public static void main(String[] args) {
        Properties pro = new Properties();

        try {
            pro.load(PropertiesEx.class.getResourceAsStream("Properties.properties"));
        } catch (IOException ex) {
            throw new RuntimeException(ex);
        }

        //주어진 키에 대한 값 읽기
        String driver = pro.getProperty("diver");
        String url = pro.getProperty("url");
        String username = pro.getProperty("username");
        String password = pro.getProperty("password");
        String admin = pro.getProperty("admin");

        //값 출력
        System.out.println("driver: "+ driver);
        System.out.println("url :" + url);
        System.out.println("usrname : "+username);
        System.out.println("password : "+password);
        System.out.println("admin : "+admin);

    }

}

driver=oracle.jdbc.OracleDriver
url=jdbc:oravle:thin:@localhost:1521:orcl
username=scott
password=tiger
admin=\uD64D\uAe38\uB3D9

 

5.Treeset

public class TreeSetEx {

    public static void main(String[] args){
     TreeSet<Integer> scores = new TreeSet<>();

     //Integer 객체 저장
        scores.add(87);
        scores.add(98);
        scores.add(75);
        scores.add(95);
        scores.add(80);

      //정렬된 Integer 객체를 하나씩 가져오기
        for(Integer s : scores){
            System.out.println(s +" ");
        }
        System.out.println("\n");

        //특정 Integer 객체 가져오기
        System.out.println("가장 낮은 점수:" + scores.first());
        System.out.println("가장 높은 점수:" + scores.last());
        System.out.println("95점 아래:" + scores.lower(95));
        System.out.println("95점 위:" + scores.higher(95));
        System.out.println("95점이거나 바로 아래 점수:" + scores.floor(95));
        System.out.println("85점이거나 바로 위의 점수:" + scores.ceiling(85)+"\n");

        //내림차순 정렬하기
        NavigableSet<Integer> descendingScore = scores.descendingSet();
        for(Integer s: descendingScore){
            System.out.println(s +" ");
        }
        System.out.println("\n");

        //범위검색 (80 <=)
        NavigableSet<Integer>rangeSet = scores.tailSet(80,true);
        for(Integer s : rangeSet){
            System.out.println(s +" ");
        }
        System.out.println("\n");

        //범위 검색(80 <= score < 90)
        rangeSet = scores.subSet(80,true,90,false);
        for(Integer s : rangeSet){
            System.out.println(s +" ");
        }
    }
}

 

6. TreeMap

 

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

        TreeMap<String,Integer> treeMap = new TreeMap<>();

        //엔트리 저장
        treeMap.put("apple",10);
        treeMap.put("forever",60);
        treeMap.put("description",40);
        treeMap.put("ever",50);
        treeMap.put("zoo",80);
        treeMap.put("base",20);
        treeMap.put("guess",70);
        treeMap.put("cherry",30);

        //정렬된 엔트리 하나씩 가져오기
        Set<Map.Entry<String,Integer>> entrySet = treeMap.entrySet();
        for(Map.Entry<String,Integer> entry : entrySet){
            System.out.println(entry.getKey() + "-" + entry.getValue());
        }
        System.out.println();

        //특정 키에 대한 값 가져오기
        Map.Entry<String,Integer> entry = null;
        entry = treeMap.firstEntry();
        System.out.println("제일 앞 단어" + entry.getKey() + "-" + entry.getValue());
        entry = treeMap.lastEntry();
        System.out.println("제일 뒤 단어" + entry.getKey() + "-" + entry.getValue());
        entry = treeMap.lowerEntry("ever");
        System.out.println("ever 앞 단어" + entry.getKey() + "-" + entry.getValue()+"\n");


        //내림차순으로 정렬하기
        NavigableMap<String,Integer> descendingMap = treeMap.descendingMap();
        Set<Map.Entry<String,Integer>> descendingEntrySet = descendingMap.entrySet();
        for(Map.Entry<String,Integer> e : descendingEntrySet){
            System.out.println(e.getKey() +"-" + e.getValue());
        }
        System.out.println();

        //범위 검색
        System.out.println("[c~h 사이의 단어 검색하기]");
        NavigableMap<String,Integer> rangeMap = treeMap.subMap("c",true,"h",false);
        for(Map.Entry<String,Integer> e : rangeMap.entrySet()){
            System.out.println(e.getKey() +" - " + e.getValue());
        }

    }

}