问类方法返回0

EN

public class Tools {

    // Instance variables
    private String type;
    private int age;
    private int eol;
    private Double lifeLeft;

    // Constructor
  public Tools(String type, int age, int eol) {
    this.type = type;
    this.age = age;
    this.eol = eol;
  }

  public String toString() {
    return type + " has reached " + lifeLeft() + "% of its life expectancy.";
  }

  public Double lifeLeft() {
    lifeLeft = (double)((this.age / this.eol) * 100);
    return lifeLeft;
  }
}

public class Wrench extends Tools {

  // Instance variables
  private Double capacity;

  // Constructor
  public Wrench(String type, int age, int eol, Double capacity) {
    super(type, age, eol);
    this.capacity = capacity;
  }

  public String toString() {
    return "Your " + capacity + "\" " + super.toString();
  }
}