java Collection

http://cafe.daum.net/ComputerScience1 다음 ConputerScience 카페에서 퍼온 내용.
이번에 작업하면서 많은 도움을 받았다. 굿!!

java.util.* 콜렉션 사용하기 ArrayTest:                                     int [] values = new int[3];                             // init              Arrays.fill(values, 0);                             values[0] = 2; values[1] = 1; values[2] = 3;                             // .length를 이용하여 for문을 사용하는 방법 대신, collection 이용              for(int oneElem : values){                     System.out.println(oneElem);              }                                  // compare              int [] values2 = { 1, 1, 3 };              if(java.util.Arrays.equals(values, values2)) {                     System.out.println("equal");              } else {                     System.out.println("not equal");              }                             // sort              Arrays.sort(values);                             // search              int [] values3 = { 10, 5, 6, 8, 7, 2, 1};              java.util.Arrays.sort(values3);              int position = java.util.Arrays.binarySearch(values3, 7);              System.out.println("found value: "+values3[position]);                               Vector: ArrayList와 Vector가 유사하지만 ArrayList는 다중 쓰레드에서 안저하지 않음              String [] str = {"test1", "test2"};                             // create Vector<String> vValue = new Vector<String>( java.util.Arrays.asList(str));                             // add a value              vValue.add("test5");                                   // add array              // List<String> nameList = java.util.Arrays.asList(addStr);              String [] addStr = {"test4", "test3"};              vValue.addAll(Arrays.asList(addStr));              System.out.println(vValue.lastElement());                                 // traverse by collection              for(String oneElem:vValue){                     System.out.println(oneElem);              }                             // traverse by Iterator              System.out.println("Vector Elements");              Iterator<String> iter = vValue.iterator();               while(iter.hasNext()) {                     System.out.println(iter.next());              }                             // get subList              List<String> subList = vValue.subList(2,3);                                            // sort: asc              System.out.println("Vector Sort Asc");              Collections.sort(vValue);              for(String oneElem:vValue){                     System.out.println(oneElem);              }                             // sort: desc              System.out.println("Vector Sort Desc");              Comparator<String> r = Collections.reverseOrder();              Collections.sort(vValue, r);              for(String oneElem:vValue){                     System.out.println(oneElem);              }                             // remove              vValue.remove(1);                // remove second element              vValue.removeAllElements();      // remove all element                             System.out.println("IsEmpty: "+vValue.isEmpty());                             System.out.println("Vector<UserClas> Test:");              Vector<Person> personVector = new Vector<Person>();              personVector.add(new Person("f1","kim"));              personVector.add(new Person("f2","park"));              personVector.add(new Person("f3","lee"));                             Collections.sort(personVector);              for(Person oneElem:personVector){                     System.out.println(oneElem);              }                         Stack:              Stack<String> sValue = new Stack<String>();                             sValue.push("stack1");              sValue.push("stack2");              sValue.push("stack3");                             // shuffle for fun              Collections.shuffle(sValue);                              while(!sValue.empty()){                     System.out.println(sValue.pop());              }                         HashMap:              // HashMap<Key, Value>              HashMap<String,Integer> aMap = new HashMap<String,Integer>();                       // if a key already exists, replace current value with new value              // key: String's hashCode() method              aMap.put("1st", new Integer(100));              aMap.put("2nd", new Integer(200));              aMap.put("3nd", new Integer(300));              aMap.put("4nd", new Integer(400));                             // get              Integer firstValue = aMap.get("1st");              System.out.println("firstValue: "+firstValue);                             // remove              Integer removeVal!ue = aMap.remove("4nd");              System.out.println("removeVal!ue: "+removeVal!ue);                             // replace              Integer oldValue = aMap.put("2nd", new Integer(210));              System.out.println("oldValue: "+oldValue + ", newValue:" +                                                      aMap.get("2nd"));                             // traverse key              System.out.println("Key: ");              Set<String> keys = aMap.keySet();              for(String key : keys) {                     System.out.println(key);              }                             // traverse value              System.out.println("Values: ");              Collection<Integer> collection = aMap.values();              for(Integer i : collection) {                     System.out.println(i);              }                             // traverse entry(key,value pair)              System.out.println("Values: ");              Set<Map.Entry<String, Integer>> entries = aMap.entrySet();              for(Map.Entry<String, Integer> i : entries) {                     System.out.println("Key:" + i.getKey() +", Value:" + i.getValue());              }                             // get Sorted Values              System.out.println("Sorted Values: ");              LinkedList<Integer> values = new LinkedList<Integer>(aMap.values());              Collections.sort(values); // Sort the entries              for(Integer entry : values) {                     System.out.println(entry);              }          PriorityQueue:                             // asc ordered queue              Queue<String> queue = new PriorityQueue<String>();                              queue.add("item5");              queue.add("item7");              queue.add("item3");              queue.add("item1");                             // traverse              for(String queueItem:queue){                     System.out.println(queueItem);              }              // extract elements by priority              while(!queue.isEmpty()){                     System.out.println(queue.remove());              }          Comparable 클래스: Vector<T> 콜렉션에서 타입 T로 사용자 정의 클래스를 사용하면서 콜렉션의 정렬 메소드를 사용하려면 Comparable<T>를 구현하여야 함. public class Person implements Comparable<Person>{        private String firstName;        private String lastName;                 // Constructor        public Person(String firstName, String lastName) {              this.firstName = firstName;              this.lastName = lastName;        }                 public String toString() {              return firstName + ": " + lastName;        }        // Compare Person objects        public int compareTo(Person person) {              // -: this.lastName, person.lastName, 0: same, +:person.lastName, // this.lastName              int result = lastName.compareTo(person.lastName);                             if( result == 0){                     // if it has same last name, compare first name                     return firstName.compareTo(((Person)person).firstName);              }              // otherwise              return result;                       } } Collection Algorithm: 콜렉션 알고리즘은 Collections.메소드(…) 형태로 사용하면 됨 sort() shuffle() reverse() fill() copy() swap() addAll() binarySearch() frequency() disjoint() min() max()