Java - how much string concat should encourage the use of StringBuilder?


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  • StringBuilder vs String concatenation in toString() in Java 17 answers

I understand that StringBuilder should be used for concatenating multiple strings rather than using +. My question is what is the cut off point?

I have been told that if concatenating 4 or more strings you should use the StringBuilder.append(), and for anything else, use +. Is that the case? or is the point at which stringbuilder is more efficient more than 4?

As of Java 1.5, the compiler automatically uses StringBuilder when + is used in the source.

From the Javadoc for String:

The Java language provides special support for the string concatenation operator ( + ), and for conversion of other objects to strings. String concatenation is implemented through the StringBuilder(or StringBuffer) class and its append method.