Question

someString[someRandomIdx] = 'g';

will give me an error.

How do I achieve the above?

Answer 1

If it is of type string then you can’t do that because strings are immutable – they cannot be changed once they are set.

To achieve what you desire, you can use a StringBuilder

StringBuilder someString = new StringBuilder("someString");

someString[4] = 'g';

Update

Why use a string, instead of a StringBuilder? For lots of reasons. Here are some I can think of:

• Accessing the value of a string is faster.
• strings can be interned (this doesn’t always happen), so that if you create a string with the same value then no extra memory is used.
• strings are immutable, so they work better in hash based collections and they are inherently thread safe.