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