Java中toString（）中的StringBuilder vs String串聯

問題：

Given the 2 toString() implementations below, which one is preferred: 給定如下2個toString()實現，首選其中一種：

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

or 要麼

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

? ？

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 ? 更重要的是，給定只有3個屬性，這可能沒有什麼區別，可是何時您將從+ concat切換到StringBuilder ？

---

解決方案：

參考一： https://stackoom.com/question/6Qf7/Java中toString-中的StringBuilder-vs-String串聯
參考二： https://oldbug.net/q/6Qf7/StringBuilder-vs-String-concatenation-in-toString-in-Java