java集合的使用方法和简单实例

//classclass Clerk{private String name;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}private int age;public Clerk(String name,int age){this.name=name;this.age=age;}public Clerk(){}}public void arraylist(){//第一种集合 ArrayListArrayList al = new ArrayList();//显示al长度//System.out.println("al的默认长度是："+al.size());//向al中加入数据Clerk ck1 = new Clerk("宋江",45);Clerk ck2 = new Clerk("吴用",40);Clerk ck3 = new Clerk("卢俊义",44);Clerk ck4 = new Clerk("林冲",30);//将ck1加入到al等al.add(ck1);al.add(ck2);al.add(ck3);al.add(ck4);System.out.println("现在的al的默认长度是："+al.size());for(int i=0;i<al.size();i++){Clerk ck = (Clerk)al.get(i);System.out.println("al的第"+i+"个元素是："+ck.getName());}}//vector向量的用法，和ArrayList完全一致，区别在于：//vector是同步的（安全性更高），ArrayList是异步的；//vector缺省情况自动增长原来一倍的数组长度，ArrayList增长原来的50%public void vector(){Vector vt = new Vector();Clerk ck5 = new Clerk("阮小二",30);Clerk ck6 = new Clerk("阮小五",28);Clerk ck7 = new Clerk("阮小七",26);vt.add(ck5);vt.add(ck6);vt.add(ck7);for(int i=0;i<vt.size();i++){Clerk ck = (Clerk)vt.get(i);}}//hashmap的用法public void hashmap(){HashMap hm = new HashMap();Clerk ck8 = new Clerk("解珍",24);Clerk ck9 = new Clerk("解宝",22);//按键值存储内容，键值重复则替换原有内容。hm.put("user1", ck8);hm.put("user2", ck9);//判断是否有键值，然后取出对应的内容if(hm.containsKey("user2")){Clerk ck = (Clerk)hm.get("user2");System.out.println("有此人，名叫："+ck.getName());}//hashmap遍历，所有的key和value，使用迭代器。Iterator it = hm.keySet().iterator();while(it.hasNext()){//取keyString key = it.next().toString();//用key取值Clerk ck = (Clerk)hm.get(key);System.out.println("---："+ck.getName());}}//hashtable的用法，和hashmap完全一致。//区别在于hashtable的同步性和线程安全性，hashmap没有同步和线性安全特性，但性能优于hashtable。//hashmap可以存null，hashtable不行。public void maptable(){Hashtable ht = new Hashtable();}