StringBuilder vs Java中toString（）的字符串连接 [英] StringBuilder vs String concatenation in toString() in Java

问题描述

鉴于下面的2 toString（）实现，首选哪一个：

Given the 2 toString() implementations below, which one is preferred:

public String toString(){
    return "{a:"+ a + ", b:" + b + ", c: " + c +"}";
}

或

public String toString(){
    StringBuilder sb = new StringBuilder(100);
    return sb.append("{a:").append(a)
          .append(", b:").append(b)
          .append(", c:").append(c)
          .append("}")
          .toString();
}

？

更重要的是，鉴于我们只有3个属性，它可能没有什么区别，但你会在什么时候从 + concat切换到 StringBuilder ？

More importantly, given we have only 3 properties it might not make a difference, but at what point would you switch from + concat to StringBuilder?

推荐答案

版本1更可取，因为它更短且编译器实际上将其转换为版本2 - 没有性能差异无论如何。

Version 1 is preferable because it is shorter and the compiler will in fact turn it into version 2 - no performance difference whatsoever.

更重要的是，鉴于我们只有3
属性，它可能不会产生
的差异，但是在什么你点
从concat切换到builder吗？

More importantly given we have only 3 properties it might not make a difference, but at what point do you switch from concat to builder?

在你循环连接点 - 这通常是当编译器不能单独替换 StringBuilder 时。

At the point where you're concatenating in a loop - that's usually when the compiler can't substitute StringBuilder by itself.

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