What's the Difference Between Java String Objects and Literals?

Understanding the Distinction between String Objects and Literals

When working with Java strings, it's crucial to understand the difference between a string object created using the new String() constructor and a string literal. A string literal, denoted by double quotes, refers to the actual string value and is stored in the String pool.

String Object

Using new String() creates a new string object in the heap. The constructor takes a character array or another string as an argument. The object contains its own copy of the string value, making it independent of any other string references.

String Literal

A string literal, on the other hand, is a literal representation of the string value. It is stored in the String pool, a memory area that collects String objects with identical values. This helps to optimize memory usage and improve performance.

Interning

When a string literal is encountered, Java checks the String pool to see if an existing string with the same value already exists. If found, the string literal refers to the existing string in the pool rather than creating a new object. This process is called interning.

Example

Consider the following code:

String str = new String("abc");
String str2 = "abc";

In this example, the first line creates a string object in the heap, while the second line creates a string literal. The string literal "abc" is interned, meaning it refers to the same string object in the pool that the first line created. Therefore, despite their different references, the two strings represent the same value.

Usage

Generally, it's recommended to use string literals whenever possible. They are more concise and efficient as the compiler can optimize the code by referencing strings already stored in the String pool. However, in cases where you need more control over string behavior, such as ensuring unique references or modifying the value, using new String() may be necessary.

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