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Java hashCode() An object hash code value can change in multiple executions of the same application. If two objects are equal according to equals() method, then their hash code must be same. If two objects are unequal according to equals() method, their hash code are not required to be different.
protected native Object clone() throws CloneNotSupportedException. public boolean equals(Object obj) protected void finalize() throws Throwable.
The Java hashCode() Method hashCode in Java is a function that returns the hashcode value of an object on calling. It returns an integer or a 4 bytes value which is generated by the hashing algorithm.
Hashcode is a unique code generated by the JVM at time of object creation. It can be used to perform some operation on hashing related algorithms like hashtable, hashmap etc. An object can also be searched with this unique code. Returns: It returns an integer value which represents hashCode value for this Method.
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.
Source code for Object class can be found here
This source contains implementation of getClass() method (See line 58). hashCode is defined as a function pointer JVM_IHashCode (See line 43).
JVM_IHashCode is defined in jvm.cpp. See code starting from line 504. This in turn calls ObjectSynchronizer::FastHashCode which is defined in synchronizer.cpp. See implementation of FastHashCode at line 576 and get_next_hash at line 530.
Probably, the methods are native for performance and due to practical issues w.r.t implementation.
For e.g., From javadocs, hashCode is typically implemented "by converting the internal address of the object into an integer". This internal address is not available via java sdk and will have to be implemented as a native method.
Please read Is it possible to find the source for a Java native method?. Also read this blog post Object.hashCode implementation. It gives more details. But makes a wrong assertion that hashCode is not generated from object's identity.
Hope it helps.
The information for these is in the header (for the class) or elsewhere (for the hashCode) This is not something you can implement in Java. The source for these methods is in the source for the JVM. e.g. you can download the source for OpenJDK.
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