当'new'运算符使用构造函数初始化内存时，JVM会做什么？

Question

RealEstate v = new RealEstate();

I have used this new keyword with RealEstate() . I know new allocates memory and initializes the memory using the RealEstate class constructor.

What is the JVM doing here?

Answer 1

new operator doesn't actually uses the help from constructor to allocate memory. It has nothing to do with constructor. Basically Java's version of malloc is new .

new operator:

• allocates memory for an object
• invokes object constructor
• returns reference to that memory

Constructor is executed separately to perform any operations during initialization, like allocating values to objects and variables. If no Constructor is defined, then compiler will create default constructor and will allocate default values:

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The following chart summarizes the default values for several data types. source

Data Type   Default Value (for fields)
byte            0
short           0
int             0
long            0L
float           0.0f
double          0.0d
char            '\u0000'
String          null
any object      null
boolean         false

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So, new operator only allocates memory and returns reference to that memory.

See the documentation :

The new operator instantiates a class by allocating memory for a new object and returning a reference to that memory. The new operator also invokes the object constructor.