code: public static MutableLong fromExternal(final LongSupplier s, final LongConsumer c) {
          return new MutableLong() {
              @Override
              public long getAsLong() {
                  return s.getAsLong();
              }
  
              @Override
              public Long get() {
                  return getAsLong();
              }
  
              @Override
              public MutableLong set(final long value) {
                  c.accept(value);
                  return this;
              }
          };
      }
docs: Construct a MutableLong that gets and sets an external value using the provided Supplier and Consumer
  
  e.g.
  <pre>
  {@code
  MutableLong mutable = MutableLong.fromExternal(()->!this.value,val->!this.value);
  }
  </pre>
  
  
  @param s Supplier of an external value
  @param c Consumer that sets an external value
  @return MutableLong that gets / sets an external (mutable) value