集合与map迭代

//ArrayList List list1 = new ArrayList(); Address address1 = new Address("中国","上海"); Address address2 = new Address("美国","纽约"); Address address3 = new Address("日本","冲绳"); list1.add(address1); list1.add(address2); list1.add(address3); for(int i = 0; i < list1.size();i++){ Address address = (Address)list1.get(i); System.out.println(address.getCountry()+"--------"+address.getCity()); } //LinkedList List list2 = new LinkedList(); Address address4 = new Address("中国","上海"); Address address5 = new Address("美国","纽约"); Address address6 = new Address("日本","冲绳"); list2.add(address4); list2.add(address5); list2.add(address6); for(int i = 0; i < list2.size();i++){ Address address = (Address)list2.get(i); System.out.println(address.getCountry()+"*******"+address.getCity()); } //set foreach迭代 判断非空 空指针异常 Set set1 = new HashSet(); Address address7 = new Address("中国","上海"); Address address8 = new Address("美国","纽约"); Address address9 = new Address("日本","冲绳"); set1.add(address7); set1.add(address8); set1.add(address9); for(Object obj: set1){ Address address = (Address)obj; System.out.println(address.getCountry()+"======="+address.getCity()); } //Iterator迭代 Iterator it = set1.iterator(); while(it.hasNext()){ Address address=(Address)it.next(); System.out.println(address.getCountry()+"_______"+address.getCity()); } Map map = new HashMap(); map.put("CN","中国"); map.put("US","美国"); map.put("RU","俄罗斯"); //key的集合是set System.out.println(map.keySet()); //value的集合是Collection System.out.println(map.values()); //keySet() Set key1 = map.keySet(); //循环拿到所有的键 Iterator iterator = key1.iterator(); while(iterator.hasNext()){ String key2 = (String)iterator.next(); String value = (String)map.get(key2); System.out.println(key2+"-----"+value); } //entrySet()--Set(Map.Entry) //增强for或迭代器Iterator Set  set3 = map.entrySet(); for(Object obj: set3){ String key = (String)((Map.Entry)obj).getKey(); String value = (String)((Map.Entry)obj).getValue(); System.out.println(key+"-----"+value);

}

//用keySet()也可以

Iterator it3 = set3.iterator(); while(iterator.hasNext()){ String key = (String)((Map.Entry)iterator.next()).getKey(); String value = (String)((Map.Entry)iterator.next()).getValue(); System.out.println(key+"-----"+value); }

//map.values()遍历

List valuesList = new ArrayList(map.values());

for(Object str:valuesList){

   System.out.println(str); } Set<Map.Entry<Integer, Iphone>> set = map.entrySet(); for(Map.Entry<Integer,Iphone> m: set){ System.out.print(m.getKey()+"====="); System.out.println(m.getValue()); }