Why are hashCode() and getClass() native methods?

java c++ c methods hashcode
user1391940 picture user1391940 · May 14, 2012 · Viewed 13.3k times · Source

I checked the source code of Object class where I found that method declaration of getClass() was

public final native Class<?> getClass();

And the declaration of hashCode() was 

public native int hashCode();

Why are these two methods native methods in the class and how can I get the source code of those methods?

Answer

Bhavik Ambani picture Bhavik Ambani · May 14, 2012

You can find the complete source code of the native methods here

I hope this will work for you.

These are native methods, because it has to interact with the machine. Here machine dependent code is written in the C language, which is not coming with the source package or in rt.jar of the lib location of the Java Runtime Environment (JRE).

One more reason for being native is possibly for the performance reasons. Due to the C level programming performance may be improved, hence they may have written the native code in the C language.

The methods are native because they concern native data. The hashCode method returns an integer value dependent on the internal representation of a pointer to an object on the heap. The getClass method must access the internal vtbl (virtual function table) that represents the compiled program's class hierarchy. Neither of these is possible with core Java.

Related questions

Is there a Java equivalent or methodology for the typedef keyword in C++?

Coming from a C and C++ background, I found judicious use of typedef to be incredibly helpful. Do you know of a way to achieve similar functionality in Java, whether that be a Java mechanism, pattern, or some other effective …

Read More
Interview question: Check if one string is a rotation of other string

A friend of mine was asked the following question today at interview for the position of software developer: Given two string s1 and s2 how will you check if s1 is a rotated version of s2 ? Example: If s1 = "stackoverflow" …

Read More
Tool to convert Java source to C++ source

Before someone shoots me down, I am aware of the Java to binary compilers and I'm not after one of those. I also know there will be no perfect tool that converts everything without any problems. I am aware that …

Read More