Make *(one|zero) weights singletons

[Hazem-Gamall]

Close #150

[Copilot]

Pull Request Overview

This PR standardizes the implementation of several weight and transition function classes by enforcing the singleton pattern, ensuring that only a single instance (one or zero) exists. Key changes include making public constructors private, adding @nonnull annotations on parameters, and updating string representations in toString methods.

• TransitionFunctionZero.java & TransitionFunctionOne.java: Constructors changed to private to enforce singleton usage and NonNull annotations added where needed.
• PathConditionWeightOne.java, MinDistanceWeightOne.java, DataFlowPathWeightOne.java, SetDomainZero.java, SetDomainOne.java: Constructors made private in line with the singleton approach.
• MinDistanceWeightImpl.java: Simplified the toString method by removing an instantiation of the singleton weight.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
idealPDS/src/main/java/typestate/TransitionFunctionZero.java	Constructor changed to private to enforce singleton
idealPDS/src/main/java/typestate/TransitionFunctionOne.java	Constructor made private and NonNull annotation added to extendWith parameter
boomerangPDS/src/main/java/boomerang/weights/PathConditionWeightOne.java	Constructors changed to private to support singleton pattern
boomerangPDS/src/main/java/boomerang/weights/MinDistanceWeightOne.java	Constructor made private to enforce singleton pattern
boomerangPDS/src/main/java/boomerang/weights/MinDistanceWeightImpl.java	toString method updated to remove redundant weight instantiation
boomerangPDS/src/main/java/boomerang/weights/DataFlowPathWeightOne.java	Constructor changed to private to enforce singleton
SynchronizedPDS/src/main/java/sync/pds/weights/SetDomainZero.java	Constructor made private in line with singleton usage
SynchronizedPDS/src/main/java/sync/pds/weights/SetDomainOne.java	Constructor made private to enforce the singleton design

[swissiety]

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