Java 如何通过外部类构造函数访问内部类?

Java 如何通过外部类构造函数访问内部类?,java,Java,我正在尝试使用我的主代码中的person构造函数创建一个person Person outerClass = new Person("Anon", new Date(06,03,1991), null); 但是它说它找不到上课日期。我是否正确地填充了这个构造函数并调用了类间函数 public class Person implements Cloneable { private String name; private Date born;

我正在尝试使用我的主代码中的person构造函数创建一个person

Person outerClass = new Person("Anon", new Date(06,03,1991), null);
但是它说它找不到上课日期。我是否正确地填充了这个构造函数并调用了类间函数

public class Person implements Cloneable
    {
        private String name;
        private Date born;
        private Date died;//null indicates still alive.

        public Person(String initialName, Date birthDate, Date deathDate)
        {
            if (consistent(birthDate, deathDate))
            {
                name = initialName;
                born = new Date(birthDate);
                if (deathDate == null)
                    died = null;
                else
                    died = new Date(deathDate);
             }
             else
             {
                 System.out.println("Inconsistent dates. Aborting.");
                 System.exit(0);
             }
        }
       private class Date
        {
            private String month;
            private int day;
            private int year; //a four digit number.

            public Date( )
            {
                month = "January";
                day = 1;
                year = 1000;
            }

            public Date(int monthInt, int day, int year)
            {
                setDate(monthInt, day, year);
            }

因为您的需求需要一个内部类,所以让我们把
Date
作为
Person
的内部类是否合适的问题放在一边

它找不到类
日期
,因为它是私有的。然而,即使它是公共的,您仍然无法实例化它,因为您首先需要一个
人的实例。一种方法是从构造函数中删除
Date
参数,并改用mutators。e、 g:

public class Person {
    private final String name;
    private Date birthDate;

    public class Date {
        private final int year, month, day;

        public Date(final int year, final int month, final int day) {
            this.year = year;
            this.month = month;
            this.day = day;
        }

        public String toString() {
            // look at me, I can access attributes of the enclosing Person
            return name + " is associated with the year " + year;
        }
    }

    public Person(final String name) {
        this.name = name;
    }

    public void setBirthDate(final Date birthDate) {
        this.birthDate = birthDate;
    }

    public static final void main(final String... arguments) throws Exception {
        final Person person = new Person("name");
        final Date birthDate = person.new Date(2015, 11, 9);
        person.setBirthDate(birthDate);
    }
}
但是,如果内部类独立于外部类的实例存在是有意义的,那么它应该是静态的。这将允许您自己实例化
日期
,而无需现有的
人员
。e、 g:

public class Person {
    private final String name;
    private final Date birthDate;

    public static class Date {
        private final int year, month, day;

        public Date(final int year, final int month, final int day) {
            this.year = year;
            this.month = month;
            this.day = day;
        }

        public String toString() {
            // I do not know about any Person
            return "year: " + year;
        }
    }

    public Person(final String name, final Date birthDate) {
        this.name = name;
        this.birthDate = birthDate;
    }

    public static final void main(final String... arguments) throws Exception {
        final Person person = new Person("name", new Date(2015, 11, 9));
    }
}

注意,这在功能上与将
Date
声明为自己的顶级类相同,只是现在完全限定的类名以“Person.Date”结尾。

为什么以万圣之名将Date作为私有内部类??为什么不简单地将其作为一个独立的公共类(尽管更改其名称以避免与
java.util.Date
混淆)?这也是我的想法,但作业要求它:/Show实际的完整要求。你可能误解了它们。你对内部类了解多少?内部类需要其声明类的实例。那么,在不引用
newperson
实例的情况下,如何创建
newdate
实例呢?重做类Person,使类日期成为类Person的私有内部类。另外,做一个合适的测试程序。