1、定义一个接口Compartor，包含三个方法： ① boolean greater(Object a); 比较两对象的大小关系，如果当前对象大于a，则返回true，否则返回false ② boolean equal(Object a); 比较两对象的大小关系，如果当前对象等于a，则返回true，否则返回false ③ boolean less(Object a); 比较两对象的大小关系，如果当前对象小于a，则返回true，否则返回false 2、定义一个学生类Student实现上述接口，类成员包含学生的姓名、年龄，对于学生进行判断大小的依据是年龄。 3、定义一个圆类Circle实现上述接口，类成员包含圆的半径，对于圆进行判断大小的依据是面积。 4、定义一个车类Car实现上述接口，类成员包含车的品牌型号、价格，对于车进行判断大小的依据是价格。 5、jAVA程序进行测试。

以下是实现上述要求的代码：

Compartor接口：

public interface Compartor {
    boolean greater(Object a);
    boolean equal(Object a);
    boolean less(Object a);
}

Student类：

public class Student implements Compartor {
    private String name;
    private int age;

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

    @Override
    public boolean greater(Object a) {
        if(a instanceof Student) {
            Student s = (Student) a;
            return this.age > s.age;
        }
        return false;
    }

    @Override
    public boolean equal(Object a) {
        if(a instanceof Student) {
            Student s = (Student) a;
            return this.age == s.age;
        }
        return false;
    }

    @Override
    public boolean less(Object a) {
        if(a instanceof Student) {
            Student s = (Student) a;
            return this.age < s.age;
        }
        return false;
    }
}

Circle类：

public class Circle implements Compartor {
    private double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    @Override
    public boolean greater(Object a) {
        if(a instanceof Circle) {
            Circle c = (Circle) a;
            return this.getArea() > c.getArea();
        }
        return false;
    }

    @Override
    public boolean equal(Object a) {
        if(a instanceof Circle) {
            Circle c = (Circle) a;
            return this.getArea() == c.getArea();
        }
        return false;
    }

    @Override
    public boolean less(Object a) {
        if(a instanceof Circle) {
            Circle c = (Circle) a;
            return this.getArea() < c.getArea();
        }
        return false;
    }

    private double getArea() {
        return Math.PI * radius * radius;
    }
}

Car类：

public class Car implements Compartor {
    private String brand;
    private double price;

    public Car(String brand, double price) {
        this.brand = brand;
        this.price = price;
    }

    @Override
    public boolean greater(Object a) {
        if(a instanceof Car) {
            Car c = (Car) a;
            return this.price > c.price;
        }
        return false;
    }

    @Override
    public boolean equal(Object a) {
        if(a instanceof Car) {
            Car c = (Car) a;
            return this.price == c.price;
        }
        return false;
    }

    @Override
    public boolean less(Object a) {
        if(a instanceof Car) {
            Car c = (Car) a;
            return this.price < c.price;
        }
        return false;
    }
}

测试代码：

public class Test {
    public static void main(String[] args) {
        Student s1 = new Student("Tom", 18);
        Student s2 = new Student("Jerry", 20);
        System.out.println("s1 > s2: " + s1.greater(s2));
        System.out.println("s1 == s2: " + s1.equal(s2));
        System.out.println("s1 < s2: " + s1.less(s2));

        Circle c1 = new Circle(3);
        Circle c2 = new Circle(4);
        System.out.println("c1 > c2: " + c1.greater(c2));
        System.out.println("c1 == c2: " + c1.equal(c2));
        System.out.println("c1 < c2: " + c1.less(c2));

        Car car1 = new Car("BMW", 300000);
        Car car2 = new Car("Audi", 250000);
        System.out.println("car1 > car2: " + car1.greater(car2));
        System.out.println("car1 == car2: " + car1.equal(car2));
        System.out.println("car1 < car2: " + car1.less(car2));
    }
}

输出结果：

s1 > s2: false
s1 == s2: false
s1 < s2: true
c1 > c2: false
c1 == c2: false
c1 < c2: true
car1 > car2: true
car1 == car2: false
car1 < car2: false