Java遍历Set集合
1、迭代器遍历:
Set<String> set = new HashSet<String>();
Iterator<String> it = set.iterator();
while (it.hasNext()) {
String str = it.next();
System.out.println(str);
}
2、for循环遍历:
for (String str : set) {
System.out.println(str);
}
3、优点还体现在泛型 假如 set中存放的是Object
Set<Object> set = new HashSet<Object>();
for循环遍历:
for (Object obj: set) {
if(obj instanceof Integer){
int aa= (Integer)obj;
}else if(obj instanceof String){
String aa = (String)obj
}
........
}
Java中遍历Map
Map<String, String> map = new HashMap();
map.put("郑州", "河南");
map.put("长沙", "湖南");
//第一種
Set<String> set = map.keySet(); //取出所有的key值
for (String key:set) {
System.out.println("第一种:"+map.get(key));
}
//第二种
Set<Map.Entry<String, String>> entryseSet=map.entrySet();
for (Map.Entry<String, String> entry:entryseSet) {
System.out.println("第二种:"+entry.getKey()+":"+entry.getValue());
}
//第三种
Iterator it = map.keySet().iterator();
while(it.hasNext()){
//int key = (Integer) it.next();
String value = map.get(it.next());
System.out.println("第三种:"+value);
}
天涯雪