Two tier clusters for representation of objects in Java programming environments

• US 7,036,120 B2
• Filed: 07/31/2001
• Issued: 04/25/2006
• Est. Priority Date: 07/31/2001
• Status: Active Grant

• Current Assignee: Oracle America, Inc. (Oracle Corporation)
• Original Assignee: Sun Microsystems Incorporated (Oracle Corporation)
• Inventors: Sokolov, Stepan, Wallman, David
• Primary Examiner(s): Zhen, Wei Y.
• Application Number:
  US09/919,743
• Publication Number:
  US 20030028865A1
• Time in Patent Office: 1,729 Days
• Field of Search: 717/149, 717/136, 717/127, 717114-118, 717/148, 717/153, 717162-167, 719/316, 719/330, 707/206
• US Class Current: 717/166
• CPC Class Codes: G06F 9/4488 Object-oriented

Abstract

Improved techniques for representation of objects in a Java™ programming environment are disclosed. The techniques are highly suitable for representation of Java™ objects inside virtual machines, especially those that operate with limited resources (e.g., embedded systems). A cluster of Java™ object representations is disclosed. Each of the Java™ object representations provide a reference to a Java™ object and a reference to the class associated with the Java™ object. Accordingly, a two-tier representation is provided which allows efficient implementation of applications which need to access information regarding both Java™ objects and classes. As a result, quick access to information regarding Java™ objects can be achieved.

Claims

1. In a Java™

computing environment, a method of identifying active Java™

objects and active Java™

classes by a virtual machine at runtime during garbage collection, said method comprising;

generating and loading in the virtual machine prior to execution time a cluster of Java™

object representations which are sequentially represented inside the virtual machine, wherein each of said Java™

object representations in said cluster consists of;

a first reference to an internal class representation of a class associated with a Java™

object, and

a second reference to instance fields associated with said Java™

object;

sequentially reading by said virtual machine at runtime said cluster of Java™

object representations;

determining by said virtual machine at runtime during garbage collection whether Java™

objects or Java™

classes are to be identified;

using said second references of said cluster during garbage collection to mark memory addresses that correspond to Java™

objects when said determining determines that Java™

objects are to be identified, thereby allowing Java™

objects to be identified at runtime by a sequential read of said cluster; and

using one or more of said first references of said cluster during garbage collection to mark memory addresses that correspond to Java™

classes when said determining determines that Java™

classes are to be identified, thereby allowing Java™

classes to be identified at runtime during garbage collection by a sequential read of said cluster, wherein said first reference is a direct reference to said internal class representation of said Java™

object.

2. A method as recited in claim 1,

wherein said second reference is a reference to an array of references, and

wherein each reference in said array of references is a reference to an instance field associated with said Java™

object.

3. A method as recited in claim 1, wherein said first and second references are allocated as four bytes.

4. A method as recited in claim 1, wherein said method further comprises:

removing internal class representations that have not been marked.

5. A method as recited in claim 1, wherein said method further comprises:

removing Java™

objects that have not been marked.

6. A computer readable medium including at least computer program code for identifying active Java™

objects and active Java™

classes by a virtual machine at runtime during garbage collection, comprising;

computer program code for generating and loading in the virtual machine prior to execution time a cluster of Java™

object representations which are sequentially represented inside the virtual machine, wherein each of said Java™

object representations in said cluster consists of;

a first reference to an internal class representation of a class associated with a Java™

object, and

a second reference to instance fields associated with said Java™

object;

computer program code for sequentially reading by said virtual machine at runtime during garbage collection said cluster of Java™

object representations;

computer program code for determining by said virtual machine at runtime during garbage collection whether Java™

objects or Java™

classes are to be identified;

computer program code for using said second references of said cluster during garbage collection to mark memory addresses that correspond to Java™

objects when said determining determines that Java™

objects are to be identified, thereby allowing Java™

objects to be identified at runtime by a sequential read of said cluster; and

computer program code for using one or more of said first references of said cluster during garbage collection to mark memory addresses that correspond to Java™

classes when said determining determines that Java™

classes are to be identified, thereby allowing Java™

classes to be identified at runtime during garbage collection by a sequential read of said cluster, wherein said first reference is a direct reference to said internal class representation of said Java™

object.

7. A computer readable medium as recited in claim 6,

wherein said second reference is a reference to an array of references, and

wherein each reference in said array of references is a reference to an instance field associated with said Java™

object.

8. A computer readable medium as recited in claim 7, wherein said first and second references are allocated as four bytes.

9. A computer-readable medium as recited in claim 6, further comprising:

computer program code for removing internal class representations that have not been marked.

10. A computer-readable medium as recited in claim 6, further comprising:

computer program code for removing Java™

objects that have not been marked.

11. A computer-readable medium as recited in claim 6, wherein said Java™

objects are identified for garbage collection at runtime.

12. In a Java™

computing environment, a computer system for identifying active Java™

objects and active Java™

classes by a virtual machine at runtime during garbage collection, said computer system comprising;

memory;

at least one processor which is configured to;

generate and load in the virtual machine prior to execution time a cluster of Java™

object representations which are sequentially represented inside the virtual machine, wherein each of said Java™

object representations in said cluster consists of;

a first reference to an internal class representation of a class associated with a Java™

object, and a second reference to instance fields associated with said Java™

object;

sequentially reading by said virtual machine at runtime said cluster of Java™

object representations;

determine by said virtual machine at runtime during garbage collection whether Java™

objects or Java™

classes are to be identified;

use said second references of said cluster during garbage collection to mark memory addresses that correspond to Java™

objects when said determining determines that Java™

objects are to be identified, thereby allowing Java™

objects to be identified at runtime by a sequential read of said cluster; and

use one or more of said first references of said cluster during garbage collection to mark memory addresses that correspond to Java™

classes when said determining determines that Java™

classes are to be identified, thereby allowing Java™

classes to be identified at runtime during garbage collection by a sequential read of said cluster, wherein said first reference is a direct reference to said internal class representation of said Java™

object.

13. A computer system as recited in claim 12,

wherein said second reference is a reference to an array of references, and

wherein each reference in said array of references is a reference to an instance field associated with said Java™

object.

14. A computer system as recited in claim 12, wherein said first and second references are allocated as four bytes.

15. A computer system as recited in claim 12, wherein said at least one processor is further configured to remove internal class representations that have not been marked.

16. A computer system as recited in claim 12, wherein said at least one processor is further configured to remove Java™

objects that have not been marked.