#vulnerable code 
                                public Vector4fc toImmutable() {
        if (Proxy.DISABLE_PROXIES)
            return this;
        if (proxy != null)
            return proxy;
        synchronized (this) {
            if (proxy != null)
                return proxy;
            proxy = Proxy.createVector4fc(this);
        }
        return proxy;
    } 
                            #location 5 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public Vector4fc toImmutable() {
        if (Proxy.DISABLE_PROXIES)
            return this;
        return Proxy.createVector4fc(this);
    }