相关文献：https://www.runoob.com/java/java-collections.html

1. ArrayList

• 类似动态数组

		ArrayList al = new ArrayList();System.out.println("al 的初始大小：" + al.size());// al 的初始大小：0al.add("C");al.add("A");al.add("E");al.add("B");al.add("D");al.add("F");al.add(1,"A2");System.out.println("al size: " + al.size());// al size: 7System.out.println("al 的内容：" + al);// al 的内容：[C, A2, A, E, B, D, F]al.remove("F");al.remove(2);System.out.println("al size: " + al.size());// al size: 5System.out.println("al 的内容：" + al);// al 的内容：[C, A2, E, B, D]ArrayList al1 = new ArrayList();al1.add(1);al1.add(2);al1.add(3);al1.add(4);System.out.println("al1 的内容：" + al1);// al1 的内容：[1, 2, 3, 4]Object o[] = al1.toArray();int sum = 0;for(int i = 0; i < o.length; ++i)sum += ((Integer)o[i]).intValue();System.out.println("sum: " + sum); // sum: 10

2. LinkedList

• 链表

		LinkedList ll = new LinkedList();ll.add("F");ll.add("B");ll.add("D");ll.add("E");ll.add("C");ll.addLast("Z");ll.addFirst("A");ll.add(1, 1);System.out.println(ll);// [A, 1, F, B, D, E, C, Z]ll.remove("F");ll.remove(2);System.out.println(ll);// [A, 1, D, E, C, Z]ll.removeFirst();ll.removeLast();System.out.println(ll);// [1, D, E, C]ll.set(2, "changed");System.out.println(ll);// [1, D, changed, C]

3. HashSet

• 哈希集合，无序

		HashSet hs = new HashSet();hs.add("A");hs.add("B");hs.add("C");hs.add(1);System.out.println(hs);// [A, 1, B, C] 无序

4. TreeSet

• 树set，有序

		TreeSet ts = new TreeSet();ts.add("C");ts.add("B");ts.add("D");ts.add("A");ts.add("Aa");System.out.println(ts);// [A, Aa, B, C, D] 有序

5. Iterator、ListIterator

• ListIterator 可以修改元素，可以双向遍历，是 Iterator 的扩展

		System.out.println(al);// [C, A2, E, B, D]Iterator it = al.iterator();while (it.hasNext()){Object obj = it.next();System.out.print(" "+ obj);} // 使用 iterator 遍历//  C A2 E B DSystem.out.println();ListIterator lit = al.listIterator();while(lit.hasNext()){Object obj = lit.next();lit.set(obj+"*");}System.out.println("打印修改后的内容：");it = al.iterator();while (it.hasNext()){Object obj = it.next();System.out.print(" "+ obj);} // C* A2* E* B* D*System.out.println();System.out.println("逆序输出：");while(lit.hasPrevious()){Object obj = lit.previous();System.out.print(" "+ obj);} // D* B* E* A2* C*System.out.println();

6. HashMap

		// HashMapHashMap hm = new HashMap();hm.put("Michael", 18);hm.put("Ming", 19);Set set = hm.entrySet();Iterator i = set.iterator();while(i.hasNext()){Map.Entry me = (Map.Entry) i.next();System.out.print(me.getKey() + ":");System.out.println(me.getValue());}int age = ((Integer)hm.get("Michael")).intValue();hm.put("Michael", age+2);i = set.iterator();while(i.hasNext()){Map.Entry me = (Map.Entry) i.next();System.out.print(me.getKey() + ":");System.out.println(me.getValue());}

输出：

Ming:19
Michael:18
Ming:19
Michael:20

7. TreeMap

		// TreeMapTreeMap tm = new TreeMap();tm.put(18, "Michael");tm.put(19, "Ming");tm.put(0, "Java");// valuesCollection col = tm.values();Iterator it1 = col.iterator();while(it1.hasNext()){System.out.println(it1.next());}// keySetCollection col1 = tm.keySet();Iterator it2 = col1.iterator();while(it2.hasNext()){System.out.println(it2.next());}// entrySet, K V 对Collection col2 = tm.entrySet();Iterator it3 = col2.iterator();while(it3.hasNext()){System.out.println(it3.next());}

输出：

Java
Michael
Ming
0
18
19
0=Java
18=Michael
19=Ming

8. Stack

• Stack 继承于 Vector，Vector 与 ArrayList 类似

class StackDemo{static void showpush(Stack st, int a){st.push(a);System.out.println("入栈：" + a);System.out.println(st);}static void showpop(Stack st){Integer a = (Integer) st.pop();System.out.println("出栈：" + a);System.out.println(st);}public static void main(String [] args){Stack st = new Stack();System.out.println(st);showpush(st,2);showpush(st,4);showpush(st,1);showpop(st);showpop(st);showpop(st);try{showpop(st);//空了，异常}catch (EmptyStackException e){System.out.println("异常：" + e);}}
}

输出：

[]
入栈：2
[2]
入栈：4
[2, 4]
入栈：1
[2, 4, 1]
出栈：1
[2, 4]
出栈：4
[2]
出栈：2
[]
异常：java.util.EmptyStackException

9. Properties 类

		// Properties : k v 都是字符串的 HashtableProperties capitals = new Properties();capitals.put("中国", "北京");capitals.put("日本", "东京");// capitals.put("美国", "华盛顿");Set states = capitals.keySet();String country;Iterator it4 = states.iterator();while(it4.hasNext()){country = (String) it4.next();System.out.println(country + " : " + capitals.getProperty(country));}String str = capitals.getProperty("美国", "not found");//若没有key，返回默认值 not foundSystem.out.println(str);

输出：

中国 : 北京
日本 : 东京
not found

读写简单 数据库

• 特别适合做简单数据库

class PropertiesFile{public static void main(String [] args){Properties settings = new Properties();try{settings.load(new FileInputStream("./count.txt"));}catch (Exception e){settings.setProperty("count", new Integer(0).toString());//没有文件就从0开始计数}int c = Integer.parseInt(settings.getProperty("count"))+1;System.out.println("这是第" + c + "次使用本程序！");settings.put("count", new Integer(c).toString());try{settings.store(new FileOutputStream("./count.txt"), "存储中");}catch (Exception e){System.out.println(e.getMessage());}}
}

输出：

这是第1次使用本程序！