map集合的4种遍历方法和List集合的2种遍历和迭代器Iterator的使用

Map集合的4种遍历：

方法一：keySet+for循环的形式

Set<String> keySet = map.keySet();

for (String key : keySet) {

String _value = map.get(key);

System.out.println("键：" + key + ",值：" + _value);

}

方法二：keySet+iterator

Iterator<String> iterator = keySet.iterator();

while (iterator.hasNext()) {

String key = iterator.next();

String _value = map.get(key);

System.out.println("键：" + key + ",值：" + _value);

}

方法三：entrySet()+for循环

Set<Entry<String, String>> entrySet = map.entrySet();

for (Entry<String, String> entry : entrySet) {

String key = entry.getKey();

String _value = entry.getValue();

System.out.println("键：" + key + ",值：" + _value);

}

方法四：

Iterator<Entry<String, String>> entryIterator = entrySet.iterator();

while (iterator.hasNext()) {

Entry<String, String> entry = entryIterator.next();

String key = entry.getKey();

String _value = entry.getValue();

System.out.println("键：" + key + ",值：" + _value);

}

Collection的2种遍历：

Iterator it = list.iterator();

while(it.hasNext()) {

String s =(String) it.next();

System.out.println(s);

}

for(int x=0; x<list.size(); x++) {

String s =(String) list.get(x);

System.out.println(s);

}