JVM中的字符串常量池分析 - 英文 Introduction：
The String Constant Pool in the Java Virtual Machine (JVM) is a special storage area that serves as a cache for string literals. When a string literal is created in Java code, the JVM checks the String Constant Pool to see if a string with the same content already exists. If it does, the JVM returns a reference to the existing string, avoiding the need to create a new object. This optimization helps improve performance and reduce memory usage.
The String Constant Pool is located in the heap memory in modern JVM implementations (specifically, from JDK 7 onwards). Prior to JDK 7, it was located in the PermGen space, which was part of the method area. However, due to various issues with PermGen, including its limited size and poor garbage collection performance, the String Constant Pool was moved to the heap in JDK 7.
When a class is loaded into the JVM, string literals from the class file are added to the String Constant Pool. Additionally, strings can be added to the pool dynamically during runtime through certain Java language constructs, such as string concatenation with the + operator (i
字符串长度规则n some cases) or the use of the intern() method.
It's important to note that the String Constant Pool only stores references to string objects, not the actual string data. The actual string objects are stored in the regular heap memory. The pool serves as a way to share references to these objects, reducing memory usage and improving performance by avoiding redundant string creations.
JVM中的字符串常量池分析 - 中文介绍：
Java虚拟机（JVM）中的字符串常量池是一个特殊的存储区域，用作字符串字面量的缓存。当在Java代码中创建一个字符串字面量时，JVM会检查字符串常量池，以查看是否存在具有相同内容的字符串。如果存在，JVM将返回对现有字符串的引用，从而避免创建新对象。这种优化有助于提高性能并减少内存使用。
在现代JVM实现中（特别是从JDK 7开始），字符串常量池位于堆内存中。在JDK 7之前，它位于方法区的PermGen空间中。然而，由于PermGen空间存在各种问题，包括其有限的大小和较差的垃圾回收性能，因此在JDK 7中将字符串常量池移动到了堆中。
当类被加载到JVM中时，来自类文件的字符串字面量会被添加到字符串常量池中。此外，在运行时，可以通过某些Java语言结构（如使用+运算符进行字符串连接（在某些情况下）或使用intern()方法）动态地将字符串添加到池中。
需要注意的是，字符串常量池仅存储对字符串对象的引用，而不是实际的字符串数据。实际的字符串对象存储在常规的堆内存中。该池通过共享对这些对象的引用来减少内存使用并提高性能，从而避免冗余的字符串创建。

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