[Simple Java] how to store Java arrays in memory, simplejava

[Simple Java] how to store Java arrays in memory, simplejava

Java has two types of Arrays:

• Array of basic data types;
• Object array;

When an object is created with the keyword "new", the memory space is allocated on the stack and the reference of the object is returned. This is the same for arrays, because arrays are also an object;

One-dimensional array

int[] arr = new int[3];

In the above Code, the arr variable stores the reference of the array object. If you create an integer array with a space of 10, the situation is the same, the space occupied by an array object is allocated on the stack and Its Reference is returned;

Two-dimensional array

How are two-dimensional arrays stored? In fact, there is only one-dimensional array in Java, and the two-dimensional array is an array that stores the array, the following code and:

int[ ][ ] arr = new int[3][ ];arr[0] = new int[3];arr[1] = new int[5];arr[2] = new int[4];

For multi-dimensional arrays, the truth is the same;

Where are the array objects and their references stored in the memory?

In Java, arrays are also an object, so how to store objects in memory is also applicable to arrays;

As we all know, the java runtime data zone includes the heap, JVM stack, and others. The following code is a small example. Let's take a look at how the array and Its Reference are stored in the memory.

class A {    int x;    int y;}...public void m1() {    int i = 0;    m2();}public void m2() {     A a = new A();}...

With the code above, let's call method m1 to see what happened:

When m1 is called, the stack Frame-1 is created and pushed to the stack, and the local variable I is also created within the stack Frame-1.

Then, the m2 method is called inside the m1 method. The stack Frame-2 is created and pushed to the stack. In the m2 method, A new object A is created in the heap, its reference is put into Frame-2 of the stack Frame;

The general situation of heap and stack in the memory is as follows:

Arrays are also objects, so the distribution of arrays and objects and references in memory is shown above;

 

Http://www.programcreek.com/2013/04/what-does-a-java-array-look-like-in-memory/.