Stack constant Pool

A. Some basic types of variable data and object reference variables defined in the function are allocated in the stack memory of the function.
When a variable is defined in a block of code, Java allocates memory space for the variable in the stack, and when the variable exits the scope, Java automatically frees the memory space allocated for the variable, and the memory space is immediately available for another use.

B. Heap memory is used to store objects and arrays created by new.  The memory allocated in the heap is managed by the automatic garbage collector of the Java Virtual machine.
after generating an array or an object in the heap, you can also define a special variable in the stack that is equal to the first address of the array or object in the heap memory, and this variable in the stack becomes the reference variable of the array or object. A reference variable is a name that is an array or an object, and you can use reference variables from the stack to access the arrays or objects in the heap later in your program. A reference variable is equivalent to a name that is an array or an object. A reference variable is a normal variable that is allocated in the stack when defined, and the reference variable is freed after the program runs outside its scope. While the array and the object itself are allocated in the heap, the memory occupied by the array and the object itself is not freed when the program runs beyond the block of code that uses new to produce the array or object's statement, and the array and object become garbage when no reference variable points to it, not in use, but still occupy memory space. The garbage collector takes off (releases) at a later indeterminate time. This isJavaCompare the reasons for memory.
In fact, the variables in the stack point to the variables in the heap memory, which isJavain the pointer!

        c. (constant Pool) refers to some data that is determined at compile time and is saved in the compiled. class file. In addition to the constant values (final) that contain the various basic types defined in the code (such as int, long, and so on) and object types (such as strings and arrays), there are some symbolic references that appear as text, such as the fully qualified name of the class and interface, the name and descriptor of the field, the method and the name and the descriptor The virtual machine must maintain a constant pool for each mounted type. A constant pool is an ordered set of constants used by that type, including direct constants (String,integer and floating point constants), and symbolic references to other types, fields, and methods. For a string constant, its value is in a constant pool. The Chang in the JVM exists as a table in memory, and for string types there is a fixed-length constant_string_info table for storing literal string values, note that the table stores only literal string values and does not store symbol references. In this case, there should be a clearer understanding of where the string values in the constant pool should be stored.

When the program executes, the constant pool is stored in the method area, not the heap.
The D.java heap is a run-time data area where objects are allocated space from. These objects are established through directives such as new, NewArray, Anewarray, and Multianewarray, and they do not require program code to be explicitly released. Heap is responsible for garbage collection, the advantage of the heap is the ability to dynamically allocate memory size, the lifetime does not have to tell the compiler beforehand, because it is at runtime to allocate memory dynamically, Java garbage collector will automatically take away these no longer use data. However, the disadvantage is that the access speed is slower due to the dynamic allocation of memory at run time.

Stack constant Pool