Java memory allocation

In order to improve the efficiency of the program, the Java program allocates different spaces for data:

The specific division is the following 5 memory allocation methods:

1. Stack: storage are local variables

2. Heap: stores all new things

3. Method area:

4. Local method area: (related to the system)

5. Register: (CPU use)

Local variables: Variables in the method definition or method declaration are called local variables

Features of heap memory:

1.Every new thing has an address value

2.Every variable has a default value

byte, short, int, long is 0

float, double is 0.0

char "\u0000" is equivalent to empty

The reference type is null

3. It will become garbage after use, but it will not be recycled immediately. It will be recycled when the garbage collector is idle.

Characteristics of stack memory:

The data is released when it leaves the scope

The value of the array name is the address, and the array element (that is, the array name [index ]) is the value of the data stored in the array.

int[] arr3 = arr; //This is to give the address of arr to arr3. Now the first addresses of arr and arr3 are the same.

ArrayIndexOutOfBoundsException: Array index out-of-bounds exception

Cause: A non-existent index was accessed

NullPointerException: Null pointer exception

Cause : The value of the array name is null and no longer points to the address value. And you also access its elements using the array name.

Array attribute: length, used to get the length of the array.

Format: array name.length

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