无法覆盖比较器的 compare() 方法

Question

尽管我已经实现了该方法，但我不确定为什么会出现以下错误。

在实现比较方法

时NameComparator.java中“NameComparator类型的方法compare(Student, Student)必须覆盖或实现超类型方法”

Student.java

public class Student {
    private String name;
    private int age;
    private String lesson;
    private int grade;

    public Student() {
    }

    public Student(String name, int age, String lesson, int grade) {
        super();
        this.name = name;
        this.age = age;
        this.lesson = lesson;
        this.grade = grade;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getLesson() {
        return lesson;
    }

    public void setLesson(String lesson) {
        this.lesson = lesson;
    }

    public int getGrade() {
        return grade;
    }

    public void setGrade(int grade) {
        this.grade = grade;
    }

    @Override
    public String toString() {
        return "[name=" + this.name + ", age=" + this.age + ", lesson="
                + this.lesson + ", grade=" + this.grade + "]";
    }

}

NameComparator.java

import java.util.Comparator;

@SuppressWarnings("rawtypes")
public class NameComparator implements Comparator {

// I’m getting this error for below method "The method compare(Student, Student) of type NameComparator must override or implement a super type method"

    @Override
    public int compare(Student s1, Student s2) {
        String name1 = o1.getName();
        String name2 = o2.getName();

        // ascending order (descending order would be: name2.compareTo(name1))
        return name1.compareTo(name2);
    }

}

Answer 1

改变

public class NameComparator implements Comparator {

到

public class NameComparator implements Comparator<Student> {

当您实现原始 Comparator 接口（不建议这样做）时，您的 compare 方法需要 Object 个参数。

Answer 2

Comparator<T> 接口是一个通用接口。事实上，它采用了 Comparator<Object> 的默认实现，这意味着它期望实现 public int compare(Object s1, Object s2) {。

要解决此问题，只需在 class decleration 中将 Comparator 替换为 Comparator<Student>。

Answer 3

方法声明必须如下所示：

@Override
public int compare(Object s1, Object s2) {

因为您没有在 implements 子句中添加通用类型。

将 class 声明更改为：

public class NameComparator implements Comparator<Student> {

错误将消失。

无法覆盖比较器的 compare() 方法

Unable to override compare() method of Comparator

java

comparator

Student.java

NameComparator.java