是连接一个空字符串做一个字符串转换真的那么糟吗？ [英] Is concatenating with an empty string to do a string conversion really that bad?

问题描述

假设我有两个 char 变量，后来我想将它们连接成一个字符串。这是我怎么做的：

  char c1，c2; 
 // ... 
 
 String s =+ c1 + c2; 
  

我看过有人说，+ trick是丑陋等，你应该使用 String.valueOf 或 Character.toString 。我喜欢这个结构，因为：

• 我喜欢使用语言功能而不是API调用如果可能
  
  
  
  
  • 通常情况下，语言通常比API更稳定吗？
  
  
  • 如果语言特性只隐藏API调用，那么更有理由更喜欢它！
    
    
    
    
    • 更抽象！隐藏很好！
    
    
  
  


• 我喜欢 c1 和 c2 在视觉上处于同一水平
  
  
  
  
  • String.valueOf（c1）+ c2 表明 c1
  
  
  valueOf 或 Character.toString 优先于+ ？
  
  
  

  ---

  
  
  

  琐事：在 java.lang.AssertionError ，以下行出现7次，每个类型都不同：

    this（+ detailMessage）; 
    

  
  

  解决方案

  这是Java语言中更具表达性的领域之一，+ 似乎已经根深蒂固。

  
  
  

  请参见字符串连接在JLS。

   + c1 + c2 
    > 
   
   
  等同于
    new StringBuffer ）.toString（））
   .append（new Character（c2）.toString（））。toString（）
    
   
   b $ b 
  ，除了所有的中间对象不是必要的（因此效率不是动机）。规范说，一个实现可以使用 StringBuffer 或不。由于这个特性是内置的语言，我没有理由使用更详细的形式，特别是在一个已经详细的语言。
   
  Let's say I have two char variables, and later on I want to concatenate them into a string. This is how I would do it:
  char c1, c2;
  // ...
  
  String s = "" + c1 + c2;
  I've seen people who say that the "" + "trick" is "ugly", etc, and that you should use String.valueOf or Character.toString instead. I prefer this construct because:
  
  
  I prefer using language feature instead of API call if possible
  
  
  In general, isn't the language usually more stable than the API?
  If language feature only hides API call, then even stronger reason to prefer it!
  
  
  More abstract! Hiding is good!
  
  
  I like that the c1 and c2 are visually on the same level
  
  
  String.valueOf(c1) + c2 suggests something is special about c1
  
  It's shorter.
  
  
  Is there really a good argument why String.valueOf or Character.toString is preferrable to "" +?
  
  
  
  Trivia: in java.lang.AssertionError, the following line appears 7 times, each with a different type:
      this("" + detailMessage);
  
  解决方案
  Your arguments are good; this is one of the more expressive areas of the Java language, and the "" + idiom seems well entrenched, as you discovered.
  
  See String concatenation in the JLS. An expression like
  "" + c1 + c2
  is equivalent to
  new StringBuffer().append(new Character(c1).toString())
                    .append(new Character(c2).toString()).toString()
  except that all of the intermediate objects are not necessary (so efficiency is not a motive). The spec says that an implementation can use the StringBuffer or not. Since this feature is built into the language, I see no reason to use the more verbose form, especially in an already verbose language.
  
                          
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