java development skills

1. Collection

• To use hashmap, you need to initialize the capacity. The formula is the desired map size/0.75+1
• Map traversal should use entrySet instead of keyset

  /**
  * 最常见也是大多数情况下用的最多的，一般在键值对都需要使用
   */
  Map <String,String>map = new HashMap<String,String>();
  map.put("熊大", "棕色");
  map.put("熊二", "黄色");
  for(Map.Entry<String, String> entry : map.entrySet()){
      String mapKey = entry.getKey();
      String mapValue = entry.getValue();
      System.out.println(mapKey+":"+mapValue);
  }
  9

   -----To be expanded