Java实现泛型接口

Question

package com.example;

import java.util.Arrays;

public class Main {
  
  public static void main(String[] args) {
    MyClass[] ms = {
      new MyClass("Monin",119),
      new MyClass("Annie",120),
      new MyClass("David",99)
    };
    Arrays.sort(ms);
    System.out.println(Arrays.toString(ms));
  }
}

interface Comparable<T> {
  public int compareTo(T o);
}

class MyClass implements Comparable<MyClass> {
  private String name;
  private int num;
  
  public MyClass(String name, int num) {
    this.name = name;
    this.num = num;
  }
  
  public int compareTo(MyClass m) {
    return this.name.compareTo(m.num);
  }
  
  public String toString() {
    return name + ":" + num;
  }
}

报错：

java.lang.ClassCastException: com.example.MyClass cannot be cast to java.lang.Comparable
    at java.util.ComparableTimSort.countRunAndMakeAscending(ComparableTimSort.java:320)
    at java.util.ComparableTimSort.sort(ComparableTimSort.java:188)
    at java.util.Arrays.sort(Arrays.java:1239)
    at com.example.Main.main(Main.java:13)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.duy.android.compiler.java.Java.run(Unknown Source:335)
    at com.duy.ide.javaide.run.activities.ExecuteActivity.executeDex(Unknown Source:42)
    at com.duy.ide.javaide.run.activities.ExecuteActivity.exec(Unknown Source:19)
    at com.duy.ide.javaide.run.activities.ExecuteActivity.access$100(Unknown Source:0)
    at com.duy.ide.javaide.run.activities.ExecuteActivity$1.run(Unknown Source:8)
    at java.lang.Thread.run(Thread.java:929)

怎么回事？如何改？

Answer 1

你的MyClass 需要实现的是java.lang 包下的Comparable接口，而不是你自定义的Comparable接口，把你自定义的这个 Comparable 接口删掉，重新导包就好了