Use of string concatenation within loops in JAVA

Faiz Mohammad — Sat, 14 Aug 2021 21:18:12 +0000

In Java, do you know about the pitfall of using string concatenation within loops??
Since strings are immutable in JAVA, when we try to append another char to a string, it creates a new copy of the string and updates the copy instead of the original string.😯

Example :

String s = "value";
s.concat("d");

On doing so, value of string s is not changed rather a new updated copy of string s is created in heap.
Now think, if concatenating string creates one another copy of string object, what would happen if do string concatenation within a loop.

string s = "coding";
for(int i = 0;i < 100000;i++){
   s += "java";
}

This would create 100000 new copies of string object s!!!😲😶😲

Creating 100000 copies leads to significantly impacting code performance. So you must be thinking what's the solution??
We have two alternative to tackle this issue?

🎉🎉 StringBuffer & StringBuilder 🙌🙌

Both serve the purpose of avoiding creation of string objects upon concatenation!

Example:

StringBuffer s3 = new StringBuffer("value");
String s2 = "value2";
for(int i = 0;i < 100000;i++){
   s3.append(s2); // s3 = s3 + s2;
}

In this scenario, no creation of string objects happen! Cool, isn't it?😁

Same can be achieved with StringBuilder, so what's the difference between the two then??
StringBuilder is not thread safe while StringBuffer is!

But more on threads later!! Hope you enjoyed this !!

DEV Community: Faiz Mohammad

Use of string concatenation within loops in JAVA