Question

我有这个方法，但是它返回错误MyComparator不是抽象的，并且没有超过我也尝试使用Present而不是PresentInterface的抽象方法，因为我已经在当前类中实现了当前接口。我最终想要对存在的数组列表进行排序非常感谢任何帮助，谢谢

public class MyComparator implements Comparable<PresentInterface>{
 // The name of the present, e.g. "one directions greatest hits"
 private String name;

 // The type of the present, e.g. music, sweets, dvds, games.
 private String type;

 //The cost of the present, e.g. £11.99
 private double cost;





/**
 * Sets the name of the present.
 * 
 * @param - name - the name of the present.
 */
 public void setName(String name) {
    this.name = name;
 }


 /**
 * Sets the type of the present.
 * 
 * @param - type - the type of the present.
 */
  public void setType(String type) {
     this.type = type;
  }


  /**
  * Sets the cost of the present.
 * 
 * @param - cost - the cost of the present.
 */
 public void setCost(double cost) {
    this.cost = cost;
  }


 /**
 * Gets the name of the present.
 * 
 * @return - the name of the present.
 */
 public String getName() {
    return name;
 }


 /**
 * Gets the type of the present.
 * 
 * @return - the type of the present.
 */
 public String getType() {
    return type;
 }


 /**
 * Gets the cost of the present.
 * 
 * @return - the cost of the present.
 */
 public double getCost() {
    return cost;
 }


 /**
 * Converts the fields in this present object to a nicer string representation.
 * 
 * @return - the present information in the form of a string: name - type - cost.
 */
  public String toString() {
    return name + " - " + type + " - " + cost;
 }
  @Override
  public double compare( Present a){
     return this.cost.compareTo(a.getCost());

    }

Answer 1

你要覆盖错误的方法。它应该是

@Override
public int compareTo(PresentInterface other) {
    return this.cost.compareTo(other.getCost());
}

正如fge所说，API将告诉您解决此问题和类似问题需要了解的一切。请看一下。

如果要将您的类用作Comparator，那么它应该实现Comparator接口，而不是Comparable接口。然后比较方法应该采用两个参数。否则，如果该类确实是一个Comparable，那么Comparable接口的泛型应该是类本身的泛型。

Answer 2

您应该实施public int compareTo( PresentInterface a)而不是public double compare( Present a)

可比较不会覆盖抽象方法

2 个答案: