In Java, how to append a string more efficiently? [duplicate]

Question

I wrote a Java program, in which, I need to append a string

" u13a2" to an existing one "u1234 u12de u1386 ... u15a3".

So gradually the string becomes longer and longer. I found the time spent on each appending also becomes longer and longer. Is there any way that we can improve this to some extend ?

The implementation came to my mind includes:

unicodeArray += " "+unicode; 

or

unicodeArray = unicodeArray.concat(" "+unicode); 

They gave similar performance. I think the main reason that causes these bad performance is the special type String. It creates a new object for every assignment. If you also think so, does this mean I'd better use another type, like byte array?

Answer 1

You should use the StringBuilder class.

StringBuilder stringBuilder = new StringBuilder();  stringBuilder.append("Some text"); stringBuilder.append("Some text"); stringBuilder.append("Some text");  String finalString = stringBuilder.toString(); 

In addition, please visit:

• "How Java optimize the code with StringBuilder?"
• "StringBuilder vs String concatenation in toString() in Java"