如何遍历HashMap

1.Iterator EntrySet

Iterator<Map.Entry<Integer,String>> iterator=map.entrySet().iterator;
while(iterator.hasNext()){Map.Entry<Integer,String> entry=iterator.next();System.out.println(entry.getKey());System.out.println(entry.getValue());
}

2.Iterator keySet

Iterator<Integer> iterator=map.keySet().iterator();
while(iterator.hasNext()){Integer key=iterator.next();System.out.println(key);System.out.println(map.get(key));
}

3.forEach EntrySet

for(Map.Entry<Integer,String> entry:map.entrySet()){System.out.println(entry.getKey());System.out.println(entry.getValue());
}

4.forEach keySet

for(Integer key:map.keySet()){System.out.println(key);System.out.println(map.get(key));
}

5.lambda

map.forEach((key,value)->{System.out.println(key);System.out.println(value);
});

6.Streams API单线程

map.entrySet().stream().forEach((entry)->{System.out.println(entry.getKey());System.out.println(entry.getValue());
});

7.Streams API 多线程

map.entrySet().parallelStream().forEach((entry)->{System.out.println(entry.getKey());System.out.println(entry.getValue());
});