Explain String vs StringBuilder vs SpannedString vs SpannableString vs SpannableStringBuilder vs CharSequence

• A String is immutable (ie, the text can’t change). It also doesn’t have any spans associated with it. (Spans are ranges over the text that include styling information like color, highlighting, italics, links, etc.) So you can use a String when your text doesn’t need to be changed and doesn’t need any styling.
• A StringBuilder has mutable text, so you can modify it without creating a new object. However, it doesn’t have any span information. It is just plain text. So use a StringBuilder when you need to change the text, but you don’t care about styling it.
• A SpannedString has immutable text (like a String) and immutable span information. It is a concrete implementation of the requirements defined by the Spanned interface. Use a SpannedString when your text has style but you don’t need to change either the text or the style after it is created.

Note: There is no such thing as a SpannedStringBuilder because if the text changed then the span information would also very likely have to change.

• A SpannableString has immutable text, but its span information is mutable. It is a concrete implementation of the requirements defined by the Spannable interface. Use a SpannableString when your text doesn’t need to be changed but the styling does.
• A SpannableStringBuilder has both mutable text and span information. It is a concrete implementation of the requirements defined by the Spannable and Editable interfaces (among others). Use a SpannableStringBuilder when you will need to update the text and its style.
• A CharSequence is an interface and not a concrete class. That means it just defines a list of rules to follow for any class that implements it. And all of the classes mentioned above implement it. So you can use a CharSequence when you want to generalize the type of object that you have for maximum flexibility. You can always downcast it to a String or SpannableStringBuilder or whatever later if you need to.