不能从静态上下文引用非静态方法（方法名称（））。为什么？

Question

我真的对此感到困惑！我有2个班，俱乐部和会员。在Membership中，我有方法getMonth（）；在Club中，我有joinedMonth（），它接受参数'month'--所以用户输入一个月，然后我希望它返回在该特定月份加入的成员资格。

我试图从Club类调用getMonth（）方法，这样我就可以继续比较月份的整数。但是，当我试图调用该方法时，我只得到提到的“非静态方法getMonth（）不能从静态上下文引用”。

基本上，这是什么，我该如何化解？

提前谢谢！

俱乐部：

public class Club
{
    private ArrayList<Membership> members;
    private int month;

    /**
     * Constructor for objects of class Club
     */
    public Club()
    {
        // Initialise any fields here ...

    }

    /**
     * Add a new member to the club's list of members.
     * @param member The member object to be added.
     */
    public void join(Membership member)
    {
        members.add(member);
    }

    /**
     * @return The number of members (Membership objects) in
     *         the club.
     */
    public int numberOfMembers()
    {
        return members.size();
    }


        /**
    * Determine the number of members who joined in the given month
    * @param month The month we are interested in.
    * @return The number of members
    */
    public int joinedMonth(int month){

        Membership.getMonth();

    }



}

成员资格：

public class Membership
{
    // The name of the member.
    private String name;
    // The month in which the membership was taken out.
    public int month;
    // The year in which the membership was taken out.
    private int year;

    /**
     * Constructor for objects of class Membership.
     * @param name The name of the member.
     * @param month The month in which they joined. (1 ... 12)
     * @param year The year in which they joined.
     */
    public Membership(String name, int month, int year)
        throws IllegalArgumentException
    {
        if(month < 1 || month > 12) {
            throw new IllegalArgumentException(
                "Month " + month + " out of range. Must be in the range 1 ... 12");
        }
        this.name = name;
        this.month = month;
        this.year = year;
    }

    /**
     * @return The member's name.
     */
    public String getName()
    {
        return name;
    }

    /**
     * @return The month in which the member joined.
     *         A value in the range 1 ... 12
     */
    public int getMonth()
    {
        return month;
    }

    /**
     * @return The year in which the member joined.
     */
    public int getYear()
    {
        return year;
    }

    /**
     * @return A string representation of this membership.
     */
    public String toString()
    {
        return "Name: " + name +
               " joined in month " +
               month + " of " + year;
    }
}

Answer 1

成员身份是一个类。但只有当方法是静态的时才允许调用方法。您的GetMonth方法不是静态的，因此需要Membership类的实例来调用它。您的club类中已经有一个实例列表，因此选择其中一个实例并对其调用GetMonth。