Javaでのコレクションのメソッドと反復器

しゅうごう

         :
        1.           (                    )

        2.                                  

                               

            :
            1.          
              :               (         )
            2.    

コレクションcollectionインタフェースのメソッド
集合の基本メソッド

           
     @SuppressWarnings({ "rawtypes", "unchecked" })
         
            

                   
                           


        //               

        Collection collection = new ArrayList();
        //    
        //         ?
        //ArrayList  add        
        //                 ?  ---   
        //           
        boolean b1 =  collection.add("a");
        boolean b2 =   collection.add("b");
        boolean b3 =   collection.add("c");
        //                   
        //                              
        boolean b4 =  collection.add(10);
        boolean b5 =  collection.add(true);
        boolean b6 =  collection.add('s');
        //    
        System.out.println(collection.toString());
//      System.out.println(b1);
//      System.out.println(b2);
//      System.out.println(b3);
//      System.out.println(b4);
//      System.out.println(b5);
//      System.out.println(b6);

        //       
        System.out.println(collection.size());

        //           
        boolean b7 = collection.contains("b");
        System.out.println(b7);

        //          
        boolean b8 = collection.remove(true);
        System.out.println(b8);
        //          
        System.out.println(collection);

        //         
        boolean b9 = collection.isEmpty();
        System.out.println(b9);

        //    
        collection.clear();
        System.out.println(collection);

追加

    public static void fun2() {
        Collection collection = new ArrayList();
        //   a b c d
        collection.add("a");
        collection.add("b");
        collection.add("c");
        collection.add("d");

        System.out.println(collection);
        //           


        Object[] array = collection.toArray();
        for (int i = 0; i < array.length; i++) {
            System.out.println(array[i]);
        }
        System.out.println(Arrays.toString(array));
    }

強制変換

      :                   
       Student         
                       set/get     

    public static void fun3() {
        /*
         *       
         *   3   
         *             
         */
        Collection collection = new ArrayList();

        collection.add(new Student("sxm", 15));
        collection.add(new Student("ygs", 16));
        collection.add(new Student("xsd", 17));

        //      (            )

        Object[] array = collection.toArray();
        //    
        for (int i = 0; i < array.length; i++) {
            //array[i]           Object  
            //     Student                 
            //               
            Student student = (Student)array[i];
            System.out.println(student.getName());
        }
    }

addAllメソッド

    Collection collection = new ArrayList();
        collection.add("ygs");
        collection.add("sxm");
        collection.add("dp");

        //addAll                   
        Collection collection2 = new ArrayList();
        collection2.add("y");
        collection2.add("s");
        collection2.add("d");
        collection2.addAll(collection);
        //   collection2              collection
        //collection2.add(collection);
        //     [y, s, d, ygs, sxm, dp, [ygs, sxm, dp]]

        System.out.println(collection);

        System.out.println(collection2);

containsAllメソッド

     Collection collection = new ArrayList();
        collection.add("ygs");
        collection.add("sxm");
        collection.add("dp");

        //containsAll                       true
        Collection collection2 = new ArrayList();
        collection2.add("ygs");
        collection2.add("sxm");
        collection2.add("dp");
        boolean containsAll = collection2.containsAll(collection);
        System.out.println(containsAll);

removeAllメソッド

    Collection collection = new ArrayList();
        collection.add("ygs");
        collection.add("sxm");
        collection.add("dp");

        //removeAll
        //                  
        //                         
        //            
        Collection collection2 = new ArrayList();
        collection2.add("ygs");
        collection2.add("sxm");
        collection2.add("dp");
        collection2.add("wl");
        collection2.removeAll(collection);
        System.out.println(collection2);

retainAll

    Collection collection = new ArrayList();
        collection.add("ygs");
        collection.add("sxm");
        collection.add("dp");

        //retainAll
        //                collection2 (         )
        //   collection   collection2         collection2 
        //   collection2              true
        //         false
        Collection collection2 = new ArrayList();
        collection2.add("ygs");
        collection2.add("sxm");
        collection2.add("dp");
        collection2.add("wl");      
        boolean retainAll = collection2.retainAll(collection);
        System.out.println(collection2);
        System.out.println(retainAll);
    }

反復器

    public static void fun1() {
        //          
        Collection collection = new ArrayList();
        collection.add("a");
        collection.add("b");
        collection.add("c");
        collection.add("d");

        //          
        Iterator iterator = collection.iterator();
        //           
        boolean isHasNext = iterator.hasNext();
        System.out.println(isHasNext);
        //        
        Object next = iterator.next();
        System.out.println(next);
    }

巡回集合

    public static void fun2() {
        //          
        Collection collection = new ArrayList();
        //                   
        //      next            
        collection.add("a");
        collection.add("b");
        collection.add("c");
        collection.add("d");

        Iterator iterator = collection.iterator();
        //                   
        while (iterator.hasNext()) {
            //   :               next()  
            System.out.println(iterator.next());
        }
    }

強制型変換

    public static void fun3() {
        /*
         *       
         *   3  
         *               
         */

        Collection collection = new ArrayList();
        collection.add(new Student("sxm",18));
        collection.add(new Student("ygs",19));
        collection.add(new Student("dp",20));
        //     
        Iterator iterator = collection.iterator();
        //    
        while (iterator.hasNext()) {
            //     (        )
            Object next = iterator.next();
            //   Student  (    )
            Student student = (Student)next;
            //    
            System.out.println(student.getName());
        }
    }
                                                                          Day.15