//首先新建一個map,往裏放數據
Map<String,String> map = new HashMap<String,String>();
map.put("id",“1”);
map.put(“name”,"小明");
//1.第一種是最常見的map遍歷方式
for(Entry<String,String> entry = map.entrySet()){
String key = entry.getKey();
String value = entry.getValue();
System.out.println(key+":"+value)
}
//2.該取值比較實用於去key值或者value
for(String key : map.keySet()){
System.out.println(key);
}
for(String value : map.values()){
System.out.println(value);
}
//3.實用Iterator
Iterator<Entry<String,String>> entry = map.entrySet().iterator();
while(entry.hasNext()){
Entry<String,String> en = entry.next();
System.out.println(en.getKey()+":"+en.getValue())
}
//4.通過key取值,性能比較差
for(String key : map.keySet){
String value = key.get(key)
System.out.println(key+":"+value);
}
//先聲明一個String類型的ArrayList ,放入值
List<String> list =new ArrayList<String>();
list.add("小明");
list.add("小紅");
//如果是實體類類型的List
//新建user類
User user = new User();
//實體類放值
user.setId(1);
user.setName("小明");
user.setId(2);
user.setName("小紅");
List<User> list2 =new ArrayList<User>();
//for循環遍歷
for(String a : list ){
System.out.println(a);
}
//for循環遍歷
for(User u : list2 ){
System.out.println(u.getId());
System.out.println(u.getName());
}
2.ArrayList速度快,用for循環,size爲條件遍歷
for(int i = 0 ; i < list.size() ; i++) {
system.out.println(list.get(i));
}
for(int i = 0 ; i < list.size() ; i++) {
system.out.println(list.get(i).getId());
system.out.println(list.get(i).getName());
}
3.iterator遍歷, 用迭代器迭代
Iterator it =list.iterator();
while(it.hasNext()){
System.out.println(it.next())
}