jill/src/main/java/io/github/agentsoz/jill/lang/Plan.java
public void step() {
    if (body == null || body.length == 0 || index < 0 || index >= body.length) {
      return;
    }
    body[index++].step();
  }
public void step() {
    if (body == null || body.length == 0 || index < 0 || index >= body.length) {
      return;
    }
    body[index++].step();
  }
Performs a single step of this plan, i.e., progresses this intention.