Mixing String + operator with StringBuilder

Asked Jan 22 '17 at 18:00

Active Jan 22 '17 at 18:00

Viewed 75 times

Let's say I have the following code:

String RET = System.getProperty("line.separator");
int x = 5, y = 3;

StringBuilder sb = new StringBuilder();
sb.append("Ship located at " + x + ", " + y + RET);
sb.append("Current time: " + System.nanoTime());
return sb.toString();

Will the compiler be smart and do this:

StringBuilder sb = new StringBuilder();
sb.append("Ship located at ");
sb.append(x);
sb.append(", ");
sb.append(y);
sb.append(RET);
sb.append("Current time: ");
sb.append(System.nanoTime());
return sb.toString();

Or will it be dumb and do this:

StringBuilder sb = new StringBuilder();
sb.append(new StringBuilder().append("Ship located at ").append(x).append(", ").append(y).append(RET).toString());
sb.append(new StringBuilder().append("Current time: ").append(System.nanoTime()).toString());
return sb.toString();

Or will it do something else?

asked Jan 22 '17 at 18:00

piegames

3

When you compiled your code and looked at the bytecode with `javap`, what did you find out? – Sotirios Delimanolis Jan 22 '17 at 18:02
It'll probably do the second thing. But if you were really smart your code wouldn't have mentioned `StringBuilder` at all and you just would've used +. – Louis Wasserman Jan 22 '17 at 18:07
The Java compiler does zero optimisation. Everything is done at the JIT level. So your answer is no. – Guillaume F. Jan 22 '17 at 18:11
Related: http://stackoverflow.com/questions/7586266/is-chain-of-stringbuilder-append-more-efficient-than-string-concatenation – Pshemo Jan 22 '17 at 18:13
No, the compiler will not. That's your job. – Bohemian Jan 22 '17 at 20:17

Mixing String + operator with StringBuilder

0 Answers0