创建HashMap的不同方式 [英] Different Ways of Creating HashMaps

问题描述

我最近一直在学习HashMaps，但我有一个问题，我似乎无法得到明确的答案。之间的主要区别 -

  HashMap hash1 = new HashMap（）; 
  

vs

  HashMap<，> hash1 = new HashMap<，> （）; //用任何你想要的Key和Value填充。 
  

我认为当你定义一个HashMap时，它需要Key和Value。任何帮助将非常感激。感谢您。

解决方案

这些是您拥有的选项：

J2SE< 5.0 style：

  Map map = new HashMap（）; 
  

J2SE 5.0+样式（使用泛型）：

  Map< KeyType，ValueType> map = new HashMap< KeyType，ValueType>（）; 
  

Google Guava 风格（更短更灵活）：

 地图< KeyType，ValueType> map = Maps.newHashMap（）; 
  

I've been learning about HashMaps recently but I have one question that I can't seem to get a clear answer on. The main difference between -

HashMap hash1 = new HashMap();

vs

HashMap<,>hash1 = new HashMap <,> (); //Filled in with whatever Key and Value you want. 

I thought when you define a HashMap it requires the Key and Value. Any help would be much appreciated. Thank You.

解决方案

Those are the options you have:

J2SE <5.0 style:

 Map map = new HashMap();

J2SE 5.0+ style (use of generics):

 Map<KeyType, ValueType> map = new HashMap<KeyType, ValueType>();

Google Guava style (shorter and more flexible):

 Map<KeyType, ValueType> map = Maps.newHashMap();

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