non sequitor non sequitor - 3 months ago 12
Java Question

StringBuilder vs String concatenation in toString() in Java

Given the 2

toString()
implementations below, which one is prefered:

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


or

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?

Answer

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

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?

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