How is memory organized and what is the data structure inside a string in a programming language?

In Java, strings are represented by objects of the String class, which are immutable. Inside the String object, there is a character array (char[]), where the string's characters are stored.

The structure is roughly as follows:

• Field char[] value — an array of characters that holds the string content.
• Field int hash — a cached hash code value for optimization.

Since strings are immutable, any modification results in the creation of a new object with a new character array.

Example:

String s = "hello";
// Inside s, there is a reference to the array ['h','e','l','l','o']

In newer versions of Java (starting from Java 9), an array of bytes (byte[]) with encoding information (LATIN1 or UTF16) is used for memory optimization.