#vulnerable code 
                                @Override
    public Optional<MethodUsage> solveMethodAsUsage(String name, List<TypeUsage> parameterTypes, TypeSolver typeSolver, Context invokationContext, List<TypeUsage> typeParameterValues) {
        List<MethodUsage> methods = new ArrayList<>();
        for (Method method : Arrays.stream(clazz.getDeclaredMethods()).filter((m) -> m.getName().equals(name)).sorted(new MethodComparator()).collect(Collectors.toList())) {
            if (method.isBridge() || method.isSynthetic()) continue;
            MethodDeclaration methodDeclaration = new ReflectionMethodDeclaration(method, typeSolver);
            MethodUsage methodUsage = new MethodUsage(methodDeclaration, typeSolver);
            for (int i=0;i<getTypeParameters().size();i++){
                String nameToReplace = getTypeParameters().get(i).getName();
                TypeUsage newValue = typeParameterValues.get(i);
                methodUsage = methodUsage.replaceNameParam(nameToReplace, newValue);
            }
            methods.add(methodUsage);
        }
        if (getSuperClass(typeSolver) != null) {
            ClassDeclaration superClass = (ClassDeclaration)getSuperClass(typeSolver).getTypeDeclaration();
            Optional<MethodUsage> ref = superClass.solveMethodAsUsage(name, parameterTypes, typeSolver, invokationContext, typeParameterValues);
            if (ref.isPresent()) {
                methods.add(ref.get());
            }
        }
        for (InterfaceDeclaration interfaceDeclaration : getInterfaces(typeSolver)) {
            Optional<MethodUsage> ref = interfaceDeclaration.solveMethodAsUsage(name, parameterTypes, typeSolver, invokationContext, typeParameterValues);
            if (ref.isPresent()) {
                methods.add(ref.get());
            }
        }
        Optional<MethodUsage> ref = MethodResolutionLogic.findMostApplicableUsage(methods, name, parameterTypes, typeSolver);
        return ref;
    } 
                            #location 16 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Override
    public Optional<MethodUsage> solveMethodAsUsage(String name, List<TypeUsage> parameterTypes, TypeSolver typeSolver, Context invokationContext, List<TypeUsage> typeParameterValues) {
        List<MethodUsage> methods = new ArrayList<>();
        for (Method method : Arrays.stream(clazz.getDeclaredMethods()).filter((m) -> m.getName().equals(name)).sorted(new MethodComparator()).collect(Collectors.toList())) {
            if (method.isBridge() || method.isSynthetic()) continue;
            MethodDeclaration methodDeclaration = new ReflectionMethodDeclaration(method, typeSolver);
            MethodUsage methodUsage = new MethodUsage(methodDeclaration, typeSolver);
            for (int i=0;i<getTypeParameters().size();i++){
                String nameToReplace = getTypeParameters().get(i).getName();
                TypeUsage newValue = typeParameterValues.get(i);
                methodUsage = methodUsage.replaceNameParam(nameToReplace, newValue);
            }
            methods.add(methodUsage);
        }
        if (getSuperClass() != null) {
            ClassDeclaration superClass = (ClassDeclaration)getSuperClass().getTypeDeclaration();
            Optional<MethodUsage> ref = superClass.solveMethodAsUsage(name, parameterTypes, typeSolver, invokationContext, typeParameterValues);
            if (ref.isPresent()) {
                methods.add(ref.get());
            }
        }
        for (InterfaceDeclaration interfaceDeclaration : getInterfaces()) {
            Optional<MethodUsage> ref = interfaceDeclaration.solveMethodAsUsage(name, parameterTypes, typeSolver, invokationContext, typeParameterValues);
            if (ref.isPresent()) {
                methods.add(ref.get());
            }
        }
        Optional<MethodUsage> ref = MethodResolutionLogic.findMostApplicableUsage(methods, name, parameterTypes, typeSolver);
        return ref;
    }