新手初学Java集合框架

/*

             1.添加 2.删除 3.遍历 4.判断

          */

         Collection col = new ArrayList();

         col.add( "张三" );

         col.add( "李四" );

         col.add( "王五" );

//        col.add("张三");

         System.out.println(col);

//        col.remove("张三");

//        System.out.println(col);

         for (Object o : col) {

             System.out.println(o);

         }

         System.out.println( "------------------" );

         Iterator it = col.iterator();

         while (it.hasNext()){

             String next = (String) it.next();

             System.out.println(next);

         }

         System.out.println(col.isEmpty());

         System.out.println(col.contains( "张三" ));

List list = new ArrayList();

        list.add( "java" );

        list.add( "c++" );

        list.add( 1 , "python" );

        list.add( ".net" );

        System.out.println(list.size());

        System.out.println(list.toString());

        //1.for each遍历

        System.out.println( "---------------" );

        for (Object o : list) {

            System.out.println(o);

        }

        //2.迭代器遍历

        System.out.println( "---------------" );

        Iterator iterator = list.iterator();

        while (iterator.hasNext()){

            System.out.println(iterator.next());

        }

        //3.list迭代器遍历

        System.out.println( "--------正序-------" );

        ListIterator listIterator = list.listIterator();

        while (listIterator.hasNext()){

            System.out.println(listIterator.next());

        }

        //逆序前必须先进行正序遍历，让指针指向列表最后一个元素，才能开发遍历

        System.out.println( "--------逆序-------" );

        while (listIterator.hasPrevious()){

            System.out.println(listIterator.previousIndex() + ":" +listIterator.previous());

        }

public boolean add(E e) {

         ensureCapacityInternal(size + 1 );  // Increments modCount!!增长修改个数

         elementData[size++] = e;

         return true ;

     }

? private void ensureCapacityInternal( int minCapacity) {

         if (elementData == DEFAULTCAPACITY_EMPTY_ELEMENTDATA) {

             minCapacity = Math.max(DEFAULT_CAPACITY, minCapacity);

         }

?        ensureExplicitCapacity(minCapacity);

     }

? private void ensureExplicitCapacity( int minCapacity) {

         modCount++;

?

         // overflow-conscious code

         if (minCapacity - elementData.length > 0 )

             grow(minCapacity);

     }

? private void grow( int minCapacity) {

         // overflow-conscious code

         int oldCapacity = elementData.length;

         int newCapacity = oldCapacity + (oldCapacity >> 1 );

         if (newCapacity - minCapacity < 0 )

             newCapacity = minCapacity;

         if (newCapacity - MAX_ARRAY_SIZE > 0 )

             newCapacity = hugeCapacity(minCapacity);

         // minCapacity is usually close to size, so this is a win:

         elementData = Arrays.copyOf(elementData, newCapacity);

     }

ArrayList arrayList = new ArrayList();

        Student s1 = new Student( "张三" , 18 );

        Student s2 = new Student( "李四" , 18 );

        Student s3 = new Student( "王五" , 18 );

        arrayList.add(s1);

        arrayList.add(s2);

        arrayList.add(s3);

        System.out.println(arrayList.toString());

        //删除元素（需要重写equals方法）

        arrayList.remove( new Student( "李四" , 18 ));

        System.out.println(arrayList.size());

public boolean equals(Object o) {

        if ( this == o) return true ;

        if (o == null || getClass() != o.getClass()) return false ;

        Student student = (Student) o;

        return age == student.age && Objects.equals(name, student.name);

    }

Vector vector = new Vector();

         vector.add( "java" );

         vector.add( "python" );

         vector.add( ".net" );

         System.out.println(vector.toString());

         //枚举器遍历

         Enumeration elements = vector.elements();

         while (elements.hasMoreElements()){

             System.out.println(elements.nextElement());

         }

public HashSet(){

   map = new HashMap<>();

}

HashSet<Student> set = new HashSet<>();

         Student s1 = new Student( "张三" , 18 );

         Student s2 = new Student( "李四" , 18 );

         Student s3 = new Student( "王五" , 18 );

         set.add(s1);

         set.add(s2);

         set.add(s3);

//        set.add(new Student("李四",18));

         System.out.println(set.size());

         System.out.println(set.toString());

//        set.remove(new Student("李四",18));

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

//        System.out.println(set.toString());

         for (Student student : set) {

             System.out.println(student);

         }

         System.out.println( "====================" );

         Iterator<Student> iterator = set.iterator();

         while (iterator.hasNext()){

             System.out.println(iterator.next());

         }

public boolean equals(Object o) {

         if ( this == o) return true ;

         if (o == null || getClass() != o.getClass()) return false ;

         Student student = (Student) o;

         return age == student.age && Objects.equals(name, student.name);

     }

? public int hashCode() {

         return Objects.hash(name, age);

     }

TreeSet<String> treeSet = new TreeSet<>( new Comparator<String>() {

?        @Override

         public int compare(String o1, String o2) {

              int n1 = o1.length() - o2.length();

              int n2 = o1测试数据pareTo(o2);

              return n1== 0 ?n2:n1;

          }

         treeSet.add( "zhangSan" );

         treeSet.add( "wkf" );

         treeSet.add( "asd" );

         treeSet.add( "abc" );

         treeSet.add( "ljCv" );

         treeSet.add( "liSi" );

         treeSet.add( "wanG" );

?        System.out.println(treeSet.toString());

         System.out.println(treeSet.size());

?

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

         map.put( "wkf" , "666" );

         map.put( "qwe" , "678" );

         map.put( "kfc" , "999" );

         map.put( "asd" , "694" );

         Set<String> keySet = map.keySet();

         for (String s : keySet) {

             System.out.println(s + "=" + map.get(s));

         }

         System.out.println( "===================" );

         Set<Map.Entry<String, String>> entries = map.entrySet();

         for (Map.Entry<String, String> entry : entries) {

             System.out.println(entry.getKey() + "=" + entry.getValue() );

         }

static final int DEFAULT_INITIAL_CAPACITY = 1 << 4 ; // hashMap初始容量大小16

static final int MAXIMUM_CAPACITY = 1 << 30 ; //hashMap的数组最大容量

static final float DEFAULT_LOAD_FACTOR = 0 .75f; //默认加载因子

static final int TREEIFY_THRESHOLD = 8 ; //jdk1.8开始，当链表长度大于8时，调整成红黑树

static final int UNTREEIFY_THRESHOLD = 6 ; //jdk1.8开始，当链表长度小于6时，调整成链表

static final int MIN_TREEIFY_CAPACITY = 64 ; //jdk1.8开始，当链表长度大于8时，并且集合元素个数大于等于64时调整成红黑树

transient Node<K,V>[] table; //哈希表中的数组