在满足要求的情况下，Map应尽量使用HashMap，Set应尽量使用HashSet。

        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");

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  }

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  }