In java, use anonymous inner classes to perform simpler double bracket initialization method

The editor of this article will introduce to you about the simpler double bracket initialization method using anonymous inner classes in java. Friends in need can refer to

java's collection collection framework, such as Set, map, and list do not provide any convenient methods for initialization. Every time you create a collection, you have to add the values ​​one by one. For example, the code for

is as follows:

Set<Character> letter=new HashSet<Character>();
letter.add(&#39;a&#39;);
letter.add(&#39;b&#39;);
//...

is very cumbersome.

But use anonymous inner classes. Could be a little simpler.

The code is as follows:

Set<Character> letter=new HashSet<Character>()
  {
   {
    add(&#39;a&#39;); add(&#39;b&#39;); add(&#39;c&#39;); add(&#39;d&#39;);
       add(&#39;e&#39;); add(&#39;f&#39;); add(&#39;g&#39;); add(&#39;h&#39;);
       add(&#39;i&#39;); add(&#39;j&#39;); add(&#39;k&#39;); add(&#39;l&#39;);
       add(&#39;m&#39;); add(&#39;n&#39;); add(&#39;o&#39;); add(&#39;p&#39;); 
       add(&#39;q&#39;); add(&#39;r&#39;); add(&#39;s&#39;); add(&#39;t&#39;); 
       add(&#39;u&#39;); add(&#39;v&#39;); add(&#39;w&#39;); add(&#39;x&#39;);
       add(&#39;y&#39;); add(&#39;z&#39;);
       add(&#39;A&#39;); add(&#39;B&#39;); add(&#39;C&#39;); add(&#39;D&#39;);
       add(&#39;E&#39;); add(&#39;F&#39;); add(&#39;G&#39;); add(&#39;H&#39;);
       add(&#39;I&#39;); add(&#39;J&#39;); add(&#39;K&#39;); add(&#39;L&#39;);
       add(&#39;M&#39;); add(&#39;N&#39;); add(&#39;O&#39;); add(&#39;P&#39;);
       add(&#39;Q&#39;); add(&#39;R&#39;); add(&#39;S&#39;); add(&#39;T&#39;);
       add(&#39;U&#39;); add(&#39;V&#39;); add(&#39;W&#39;); add(&#39;X&#39;);
       add(&#39;Y&#39;); add(&#39;Z&#39;);
   }
  };  //第一层括号为定义匿名内部类，第二层则为初始化模块

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