Question

我正在尝试为以下问题编写代码： WAP获得empno，DOB和少数员工的薪水。编写两个匿名内部类，一个实现一个接口，根据他们的DOB对员工进行排序;另一个匿名内部类，扩展一个类，根据他们的工资对员工进行排序。我的代码是：

 //required import statements

public class OuterClass {
    private int empno;
    private String DOB;
    private int salary;

    public OuterClass() {
        // TODO Auto-generated constructor stub
    }

    public OuterClass(int empn, String dob, int sal) {
        //code for paramaterized constructor
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        List<OuterClass> list = new ArrayList<OuterClass>();
        while (true) {
            //code for input from user and adding it in list
        }   
    }

    Employee abc = new Employee() {
        @Override
        void SalarySort(List<OuterClass> l) {
            Collections.sort(l, new Comparator<OuterClass>() {
                public int compare(OuterClass e1, OuterClass e2) {
                    return e1.salary - e2.salary;
                }
            });
            Iterator<OuterClass> itr = l.iterator();
            while (itr.hasNext()) {
                OuterClass employee = (OuterClass) itr.next();
                System.out.println("Emp no : " + employee.empno + " Emp dob : "
                        + employee.DOB + " Emp Salary : " + employee.salary);
            }
        }

    }.SalarySort(list);// compile error : create local field list

}

class Employee {
    void SalarySort(List<OuterClass> l) {

    }
}

我的问题是，我无法调用匿名类Employee的方法SalarySort，如何解决问题？

Answer 1

如果您减少非编译部分的代码，则归结为

Employee abc = new Employee() { ... }.SalarySort(list);

因此，您尝试使用方法abc返回的值初始化Employee类型的变量SalarySort()，该值返回void。

你只想要

Employee abc = new Employee() { ... };
abc.SalarySort(list);

或

new Employee() { ... }.SalarySort(list);

BTW，阅读编译器错误消息可能有助于找到问题。

另一个问题是上面的代码应该在main方法中，其中定义了list，而不是在它之外。

此外，尊重Java命名约定，并为类，方法和变量选择好名称。不要将员工称为非员工的东西。不要将XxxInnerClass命名为不是内部类的东西。

Answer 2

这个怎么样？它使用Anonymous内部类来实现接口，并且还扩展了一个类。

import java.util.Arrays;
import java.util.Comparator;

public class AnonymousInner
{
int empNo;
double salary;
MyDate dateOfBirth;
public AnonymousInner(int empNo, double salary, MyDate dateOfBirth)
{
    this.empNo = empNo;
    this.salary = salary;
    this.dateOfBirth = dateOfBirth;
}

@Override
public String toString()
{
    return "\nEmployee = " + empNo + " Salary= " + salary + " DOB= " + dateOfBirth;
}
public static void main(String[] args)
{
    AnonymousInner[] a =
    {new AnonymousInner(1, 5000, new MyDate(15, 0, 1994)), new AnonymousInner(2, 4000,
            new MyDate(15, 1, 1993)), new AnonymousInner(3, 5000, new MyDate(15, 0, 1995)),
            new AnonymousInner(4, 6000, new MyDate(16, 0, 1994)), new AnonymousInner(5, 9000,
                    new MyDate(15, 1, 1994))};

    Arrays.sort(a, new Comparator<AnonymousInner>()  //This creates anonymous class that implements an interface
    {

        @Override
        public int compare(AnonymousInner o1, AnonymousInner o2)
        {

            return ((Double) o1.salary).compareTo(o2.salary);
        }
    });
    System.out.println("Sorting on Salary");
    for (AnonymousInner s : a)
    {
        System.out.println(s);
    }

    a = new sortDOB()
    {
    }.sort(a);  //this creates Anonymous class that extends a class

    System.out.println("\nSorting on DOB\n");
    for (AnonymousInner s : a)
    {
        System.out.println(s);
    }

}

}

class sortDOB
{

public AnonymousInner[] sort(AnonymousInner[] x)
{
    int size = x.length;
    for (int i = 0; i < size; i++)
    {
        for (int j = 0; j < size - 1; j++)
        {
            int k = j + 1;
            int compare = (x[j].dateOfBirth).compareTo(x[k].dateOfBirth);
            if (compare == 1)
            {
                AnonymousInner temp = x[j];
                x[j] = x[k];
                x[k] = temp;

            }
        }
    }
    return x;
}
}

class MyDate implements Comparable<MyDate>
{
int year, month, day;
public MyDate(int day, int month, int year)
{
    this.year = year;
    this.month = month;
    this.day = day;
}

public MyDate()
{
}

@Override
public String toString()
{
    return day + "/" + month + "/" + year;
}

@Override
public int compareTo(MyDate o2)
{
    if (year == o2.year)
    {
        if (month == o2.month)
        {
            if (day == o2.day)
            {
                return 0;
            }
            else if (day < o2.day)
            {
                return -1;
            }
            else
            {
                return 1;
            }

        }
        else if (month < o2.month)
        {
            return -1;
        }
        else
        {
            return 1;
        }
    }
    else if (year < o2.year)
    {
        return 1;
    }
    else
    {
        return -1;
    }

}
}

在java中调用匿名类方法

2 个答案: