java中的集合类

List基本操作
ArrayList<String> arrayList = new ArrayList<String>();
        arrayList.add("Tom");
        arrayList.add("Jerry");
        arrayList.add("Micky");
        // 使用Iterator遍历元素
        Iterator<String> it = arrayList.iterator();
        while (it.hasNext()) {
            String str = it.next();
            System.out.println(str);
        }
        // 在指定位置插入元素
        arrayList.add(2, "Kate");
        // 通过索引直接访问元素
        for (int i = 0; i < arrayList.size(); i++) {
            System.out.println(arrayList.get(i));
        }
        List<String> subList = new ArrayList<String>();
        subList.add("Mike");
        // addAll(Collection<? extends String> c)添加所给集合中的所有元素
        arrayList.addAll(subList);
        // 判断是否包含某个元素
        if (arrayList.contains("Mike")) {
            System.out.println("Mike is include in the list");
        }

        LinkedList<String> linkedList = new LinkedList<String>();
        linkedList.addAll(arrayList);
        // 获取指定元素
        System.out.println(linkedList.get(4));
        // 获取第一个元素
        System.out.println(linkedList.getFirst());
        // 获取最后一个元素
        System.out.println(linkedList.getLast());
        // 获取并删除第一个元素
        System.out.println(linkedList.pollFirst());
        // 获取，但不移除第一个元素
        System.out.println(linkedList.peekFirst());

ArrayList添加元素的效率
ArrayList<String> arrList = new ArrayList<String>();
        long startTimeMillis, endTimeMillis;
        startTimeMillis = System.currentTimeMillis();
        for (int i = 0; i < 10000; i++) {
            arrList.add(0, "addString");
        }
        endTimeMillis = System.currentTimeMillis();
        System.out.println("ArrayList:" + (endTimeMillis - startTimeMillis)
                + "ms");

        arrList.clear();

        startTimeMillis = System.currentTimeMillis();
        for (int i = 0; i < 20000; i++) {
            arrList.add(0, "addString");
        }
        endTimeMillis = System.currentTimeMillis();
        System.out.println("ArrayList:" + (endTimeMillis - startTimeMillis)
                + "ms");

        arrList.clear();

        startTimeMillis = System.currentTimeMillis();
        for (int i = 0; i < 40000; i++) {
            arrList.add(0, "addString");
        }
        endTimeMillis = System.currentTimeMillis();
        System.out.println("ArrayList:" + (endTimeMillis - startTimeMillis)
                + "ms");

        arrList.clear();

        startTimeMillis = System.currentTimeMillis();
        for (int i = 0; i < 80000; i++) {
            arrList.add(0, "addString");
        }
        endTimeMillis = System.currentTimeMillis();
        System.out.println("ArrayList:" + (endTimeMillis - startTimeMillis)
                + "ms");

        arrList.clear();

        startTimeMillis = System.currentTimeMillis();
        for (int i = 0; i < 160000; i++) {
            arrList.add(0, "addString");
        }
        endTimeMillis = System.currentTimeMillis();
        System.out.println("ArrayList:" + (endTimeMillis - startTimeMillis)
                + "ms");

        arrList.clear();

        startTimeMillis = System.currentTimeMillis();
        for (int i = 0; i < 320000; i++) {
            arrList.add(0, "addString");
        }
        endTimeMillis = System.currentTimeMillis();
        System.out.println("ArrayList:" + (endTimeMillis - startTimeMillis)
                + "ms");

Map基本操作
HashMap<String, Integer> map = new HashMap<String, Integer>();
        // 向Map中添加元素
        map.put("Tom", 26);
        map.put("Jack", 18);
        map.put("Micky", 17);
        map.put("Kate", 15);
        // 根据Key获取Value
        System.out.println("Jack is " + map.get("Jack") + " years old");
        // 移除
        map.remove("Micky");
        // 遍历Map
        for (Entry<String, Integer> entry : map.entrySet()) {
            System.out.println("name:" + entry.getKey() + " age:"
                    + entry.getValue());
        }
        // Key相同的元素将被覆盖
        map.put("Jack", 19);
        // 根据Key获取Value
        System.out.println("Jack is " + map.get("Jack") + " years old");
        // 判断是否包含某个Key
        if (map.containsKey("Tom")) {
            System.out.println(map.get("Tom"));
        }
        // 判断是否包含某个Value
        if (map.containsValue(26)) {
            System.out.println("The map include the value 26");
        }
        // 判断map是否为空
        if (!map.isEmpty()) {
            // 获取map大小
            System.out.println("The map‘s size=" + map.size());
        }
        // 获取Key的集合
        for (String str : map.keySet()) {
            System.out.println(str);
        }

        TreeMap<String, Integer> treeMap = new TreeMap<String, Integer>();
        treeMap.putAll(map);
        // 输出内容按照key值排序
        for (Entry<String, Integer> entry : treeMap.entrySet()) {
            System.out.println("name:" + entry.getKey() + " age:"
                    + entry.getValue());
            // name:Jack age:19
            // name:Kate age:15
            // name:Tom age:26
        }

        LinkedHashMap<String, Integer> linkedHashMap = new LinkedHashMap<String, Integer>();
        // 向Map中添加元素
        linkedHashMap.put("Tom", 26);
        linkedHashMap.put("Jack", 18);
        linkedHashMap.put("Micky", 17);
        linkedHashMap.put("Kate", 15);
        // 保持了插入的顺序
        for (Entry<String, Integer> entry : linkedHashMap.entrySet()) {
            System.out.println("name:" + entry.getKey() + " age:"
                    + entry.getValue());
            // name:Tom age:26
            // name:Jack age:18
            // name:Micky age:17
            // name:Kate age:15
        }

Set基础操作
           List<Integer> list = new ArrayList<Integer>();
           list.add(3);
           list.add(4);
           HashSet<Integer> hashSet = new HashSet<Integer>();
           hashSet.add(1);
           hashSet.add(3);
           hashSet.add(2);
           hashSet.add(6);
           // 重复元素将不能被添加
           hashSet.add(3);
           // 只要有元素被添加就返回true
           if (hashSet.addAll(list)) {
               System.out.println("Add success");
           }
           // 判断是否存在某个集合
           if (hashSet.containsAll(list)) {
               System.out.println("The hashSet is contain 3 and 4");
           }
           Iterator<Integer> it = hashSet.iterator();
           while (it.hasNext()) {
               System.out.print(it.next() + " ");
               // 1 2 3 4 6
               // 看结果是被排序了，HashSet按照Hash函数排序，Integer值的HashCode就是其int值
           }
           // 换转成数组
           Object[] integers = hashSet.toArray();
           for (int i = 0; i < integers.length; i++) {
               System.out.print((Integer) integers[i]);
           }
           //移除元素
           hashSet.remove(3);
           
           TreeSet<String> treeSet = new TreeSet<String>();
           treeSet.add("C");
           treeSet.add("A");
           treeSet.add("D");
           treeSet.add("B");
           for (Iterator<String> strIt = treeSet.iterator(); strIt.hasNext();) {
               System.out.print(strIt.next());
               // ABCD 按照字母顺序
           }
           LinkedHashSet<String> linkedHashSet = new LinkedHashSet<String>();
           linkedHashSet.add("C");
           linkedHashSet.add("A");
           linkedHashSet.add("D");
           linkedHashSet.add("B");
           for (Iterator<String> linkedIt = linkedHashSet.iterator(); linkedIt
                   .hasNext();) {
               System.out.print(linkedIt.next());
               // CADB 按照插入顺序
           }