什么是 Java 字符串池，“s"是怎样的?与新字符串(“s")不同? [英] What is the Java string pool and how is "s" different from new String("s")?

问题描述

What is meant by String Pool? And what is the difference between the following declarations:

String s = "hello";
String s = new String("hello");

Is there any difference between the storing of these two strings by the JVM?

解决方案

The string pool is the JVM's particular implementation of the concept of string interning:

In computer science, string interning is a method of storing only one copy of each distinct string value, which must be immutable. Interning strings makes some string processing tasks more time- or space-efficient at the cost of requiring more time when the string is created or interned. The distinct values are stored in a string intern pool.

Basically, a string intern pool allows a runtime to save memory by preserving immutable strings in a pool so that areas of the application can reuse instances of common strings instead of creating multiple instances of it.

As an interesting side note, string interning is an example of the flyweight design pattern:

Flyweight is a software design pattern. A flyweight is an object that minimizes memory use by sharing as much data as possible with other similar objects; it is a way to use objects in large numbers when a simple repeated representation would use an unacceptable amount of memory.

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