> Another example is Specter. Specter is a generically useful library for querying and manipulating data structures

> https://github.com/redplanetlabs/specter/tree/master/src

> MutableCell.Java. 8 years ago

  package com.rpl.specter;

  public class MutableCell {
    private Object o;

    public MutableCell(Object o) {
      this.o = o;
    }

    public Object get() {
      return o;
    }

    public void set(Object o) {
      this.o = o;
    }
  }

Behold the power!