Immutable String - Problem and Solutions

In C++ String is mutable , So there won't be any Problem.

But in Java String is immutable which creates problem and we have to resolve it .

So as String is immutable , If you want to change to change the String you have to create a new String even if you want to change one character .


So if we have to do String Concatenation in Java using '+' . It will take O(N*N) time .

String Concatenation is Slow in Java compared to C++ Which is not noticeable .

In Java Concatenation happens by first allocating enough space for new string and copy the contents from old string and append to the new String.

Time Complexity for a String of length 10 and n = 10000 is :


10+10* 2 +10 * 3 + ...... + 10 * n

= 10 * n * (n+1) / 2

Which will be O(N*N).

Example :

package com.techyield.operationsinarray;

public class StringConcatenation {

public static void main(String[] args) {

String s = "";

int n = 200000;

for(int i =0 ; i< n ;i++) {

s += "hello";

}

}

}

So you want to make String Immutable to Mutable :

Check here : https://techyield.blogspot.com/2019/06/string-immutable-to-mutable-java.html