The difference between java stack and heap

1, The garbage collection mechanism only acts on the heap memory and has nothing to do with the stack memory;

2, Stack: The stack access speed is faster than the heap, and it is efficient in saving local variables and object reference values ​​

3, Heap: Save large variables

4. When the compiler processes int a = 3, it will first create a reference to the variable a in the stack, and then check whether the value 3 exists on the stack. If it does not exist, Store 3 in;
The same is true when processing b = 3, because 3 was stored before, so at this time the compiler only needs to create the variable b and point it to 3 (which is good for saving space).
At this time, a and b will point to 3 at the same time, but it does not affect their use. If a = 4; is defined at this time, 4 needs to be stored in the memory, and a points to 4. The modification of the a value will not affect the b value.

内存的划分：
1，寄存器。
2，本地方法区。
3，方法区。
4，栈内存。
    存储的都是局部变量。
    而且变量所属的作用域一旦结束，该变量就自动释放。
5，堆内存。
    存储是数组和对象(其实数组就是对象) 凡是new建立在堆中。
    特点：
    1，每一个实体都有首地址值。
    2，堆内存中的每一个变量都有默认初始化值，根据类型的不同而不同。整数是0，小数0.0或者0.0f，boolean false char '\u0000'
    3，垃圾回收机制。