是否有“最快的方式”？用Java构建字符串？ [英] Is there a "fastest way" to construct Strings in Java?

问题描述

我通常用以下方式在Java中创建一个String：

I normally create a String in Java the following way:

String foo = "123456";

但是，我的讲师坚持要求我使用格式方法形成一个字符串，如下所示：

However, My lecturer has insisted to me that forming a String using the format method, as so:

String foo = String.format("%s", 123456);

快得多。

此外，他说使用StringBuilder类的速度更快。

Also, he says that using the StringBuilder class is even faster.

StringBuilder sb = new StringBuilder();
String foo = sb.append(String.format("%s", 123456)).toString();

创建字符串的方法最快，如果有的话 ？

它们不能100％准确，因为我可能不完全记得它们。

推荐答案

如果只有一个字符串，那么：

If there is only one string then:

String foo = "123456";

最快。您会注意到 String.format 行中声明了％s％，所以我不知道看看讲师怎么可能认为这更快。另外，你有一个方法调用。

Is fastest. You'll notice that the String.format line has "%s%" declared in it, so I don't see how the lecturer could possibly think that was faster. Plus you've got a method call on top of it.

但是，如果你正在构建一个字符串，例如在for循环中，那么你我想要使​​用StringBuilder。如果您只是使用 + = ，那么每次 + = 调用code>行。 StringBuilder更快，因为它每次调用追加时都会保留一个缓冲区并附加到它。

However, if you're building a string over time, such as in a for-loop, then you'll want to use a StringBuilder. If you were to just use += then you're building a brand new string every time the += line is called. StringBuilder is much faster since it holds a buffer and appends to that every time you call append.

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