java中如何遍历Map对象的4种方法

方法一:在for-each循环中使用entry来遍历

Map<Integer,Integer> map = new HashMap<Integer,Integer>();        
for(Map.Entry<Integer,Integer> entry:map.entrySet()){    
  System.out.println("key="+entry.getKey()+",value = "+entry.getValue());    
}

方法二:在for-each循环中遍历keys或values

Map<Integer,Integer> map = new HashMap<Integer,Integer>();    
//遍历map中的键  
for(Integer key:map.keySet()){  
  System.out.println("key="+key);
}  
//遍历map中的值  
for(Integer value:map.values()){  
  System.out.println("value ="+value);
}

方法三:使用Iterator遍历

Map<Integer,Integer> map = new HashMap<Integer,Integer>();  
Iterator<Map.Entry<Integer,Integer>> entries = map.entrySet().iterator();  
while(entries.hasNext()){
  Map.Entry<Integer,Integer> entry = entries.next();  
  System.out.println("key="+entry.getKey()+"value = "+entry.getValue());  
}

方法四:不使用泛型

Map map = new HashMap();  
Iterator entries = map.entrySet().iterator();  
while(entries.hasNext()){  
  Map.Entry entry = (Map.Entry)entries.next();  
  Integer key = (Integer)entry.getKey();  
  Integer value = (Integer)entry.getValue();  
  System.out.println("key = "+key+",value = "+value);
}

关注下面微信公众号获得更多学习资源！