Map集合的四种遍历方式

Map<Integer,String> map = new HashMap<Integer,String>();
for (int i = 0; i < 10000; i++ ){
    map.put(i, "thanks");
}

/*第一种遍历*/
Iterator<Map.Entry<Integer,String>> iter = map.entrySet().iterator();
while (iter.hasNext()) {
    Map.Entry<Integer,String> entry = (Map.Entry<Integer,String>) iter.next();
    int key = entry.getKey();
    String val = entry.getValue();
    
    System.out.println(key + "=" + val + " ");
}

/*第二种遍历*/
for (Map.Entry<Integer, String> entry : map.entrySet()) {
    int key = entry.getKey();
    String val = entry.getValue();

    System.out.println(key + "=" + val + " ");
}

/*第三种遍历*/ 
Iterator<Integer> itr = map.keySet().iterator();
while (itr.hasNext()) {
     int key = itr.next();
     String val = map.get(key);

     System.out.println(key + "=" + val + " ");
}

/*第四种遍历*/
for (Integer keyset : map.keySet()) {
    int key = keyset.intValue();
    String val = map.get(key);

    System.out.println(key + "=" + val + " ");
}