Where Does Java’s String Constant Pool Live: The Heap or the Stack?

Where Does Java's String Constant Pool Live, the Heap or the Stack?

In Java, strings are stored in a special area known as the string constant pool. This pool holds all of the string literal values used in a program, such as "Hello World", and can be accessed by every variable in the program. But where does this pool of constants actually reside? Is it on the stack, or on the heap? The answer is: it depends.

When a string literal is created in Java, it is first checked to see if it already exists in the string constant pool. If so, a reference to the existing string is returned. If not, a new string object is created in the heap, and its reference is added to the string constant pool. This means that for each instance of a literal string value, only one object will be created in the heap.

However, when a string is created using a constructor or a method like String.valueOf(), the string is stored in the heap and not in the string constant pool. This means that for the same literal value, multiple objects can be created.

So, to answer the question, Java's string constant pool lives in both the stack and the heap. It is first checked in the stack, and if it doesn't exist, it is then created on the heap. As a result, literal strings are only stored once, helping to reduce memory requirements.