java - What is the difference between abstract class and interface in terms of their storage in JVM -


this question has answer here:

what difference between abstract class , interface in terms of storage in jvm. more precise jvm store interfaces memory?

warning: mentioned @assylias, mechanics specific oracle hotspot jvm.

before java8

all meta information stored in permgen, both abstract classes , interfaces. meta information includes class specific information (what fields has, parent, etc).

interface can have public static final fields, field meta information stored in permgen.

abstract class can have both static , non-static fields. however, there no difference in terms of meta information, stored in permgen too. on other hand, real object instances stored in heap both static , non-static fields.

see example

public class myclass {    public static final calendar calendar = calendar.getinstance();    private date mydate = new date(); }

field information calendar , mydate stored in permgen , real object instances stored in heap.

in java8 permgen moved inside heap space, in so-called metaspace, not see java.lang.outofmemoryerror: permgen space anymore. however, conceptual separation between meta information , object allocation memory still present.

also review @alextaylor specification quotation.


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