Hi can any java user tell what is the time complexity of += operator for string concatenation in java ? O(n^2) or O(n)

Each call to `.concat()`

or `+=`

is O(n), where n is the current length of the string.

Okay, so if I concatenate 2 strings A and B of length N and M respectively. And If I do the operation:

```
A+=B
```

then it would have a complexity of O(NM) right ?

No, sorry - I should refine my original statement: given such A and B, the complexity of

A += B is O(N + M).

Okay I see, can you suggest a way to add a character to the end of a string in O(1) time in java without using stringBuilder?

I’m not a Java guy, but no, I can’t see a way to add a `char`

to an arbitrary `java.lang.String`

in O(1).

1 Like

Okay thanks for replying

1 Like

```
String s="Jav"; char c='a';
s=s+""+c; //s="Java"
```

An example to add a character at the end.