String Literals vs. `new String()`: What's the Performance Difference?

Understanding the Distinction between String Objects and String Literals in Programming

In programming, a fundamental question often arises: what is the difference between creating a String object with new String() and using string literals directly? This question is crucial for optimizing code performance and understanding object-oriented principles.

String Literals vs. String Objects

A string literal is created by simply enclosing a sequence of characters within quotation marks, for example, "abc". In contrast, a String object is created using the new keyword and a constructor, such as new String("abc").

Interning and Object Creation

The key distinction between string literals and string objects lies in the concept of interning. When using string literals, the runtime system may intern the string. Interning involves storing only one copy of the string in memory and a reference is created pointing to it. This improves performance by reducing memory usage and increasing efficiency. However, using new String() creates a new String object on the heap, which is distinct from any previously interned strings.

Reference Comparison

Since interning occurs for string literals but not for String objects, referencing different string literals that have the same value will still point to the same object, while referencing different String objects will point to different objects. In other words, == equality for string literals checks the reference, while for String objects it checks both the reference and the value.

Performance and Optimization

In general, it is recommended to use string literals when possible. This allows the compiler to potentially intern the string, improving both readability and performance. Conversely, using new String() explicitly creates a new String object, which can lead to increased memory usage and reduced code efficiency.

By understanding the difference between string literals and string objects, programmers can optimize their code, ensure object integrity, and effectively manage memory in their applications.

The above is the detailed content of String Literals vs. `new String()`: What's the Performance Difference?. For more information, please follow other related articles on the PHP Chinese website!