Java - extends似乎是在調用其他類的構造函數

Question

我正在嘗試java，我似乎遇到了一些問題。 我似乎唯一的問題是當我添加Stars類的擴展時，構造函數似乎被調用而沒有我聲明像Stars test = new Star（）;

Knight.java

import javax.swing.JOptionPane;

public class Knight extends Stars {
    private String name;
    private int health, battles, age, gold;

    public Knight() {
        name = JOptionPane.showInputDialog("What is the knight's name?");
        String message = String.format("How much health does %s have?", name);
        health = Integer.parseInt(JOptionPane.showInputDialog(message));
        message = String.format("How many battles has %s been in?", name);
        battles = Integer.parseInt(JOptionPane.showInputDialog(message));
        message = String.format("How old is %s?", name);
        age = Integer.parseInt(JOptionPane.showInputDialog(message));
        message = String.format("How much gold does %s have?", name);
        gold = Integer.parseInt(JOptionPane.showInputDialog(message));
    }

    public String getStats() {
        // String message = 
        return String.format("\nKnight Name: %s\nKnight Health: %d\nKnight Battles: %d\nKnight Age: %d\nKnight Gold: $%d\n\n", name, health, battles, age, gold);
    }

}

Stars.java導入javax.swing.JOptionPane;

public class Stars {
    private int rows, cols;
    private String skyScape = new String();

    public Stars() {
        rows = Integer.parseInt(JOptionPane.showInputDialog("How many rows of stars are there?"));
        cols = Integer.parseInt(JOptionPane.showInputDialog("How many columns of stars are there?"));
        for (int count = 0; count < rows; ++count) {
            if ((count % 2) == 1) {
                skyScape += " *";
            } else {
                skyScape += "*";
            }
            for (int colCount = 1; colCount < cols; ++colCount) {
                    skyScape += " *";
                    if (colCount == cols - 1) {
                        skyScape += "\n";
                    }
            }
        }
    }

    public int getRows() {
        return rows;
    }

    public int getCols() {
        return cols;
    }

    public String getSky() {
        return skyScape;
    }
}

任何幫助，將不勝感激！

Answer 1

Java要求每個構造函數（Object除外）都調用一些超類構造函數，以確保初始化超類中包含的數據。 如果不顯式調用超類構造函數，編譯器將插入對超類的默認（零參數）構造函數的隱式調用。

Answer 2

您的構造函數調用基類構造函數。 否則，基類的成員將無法使用。

Answer 3

沒有任何錯誤。 每當instantiate化子類時， 必須在執行子類構造函數之前調用超類構造函數。

Answer 4

當你正在擴展Star類時， Knight extends Stars ，Stars類也被加載到Knight類中，因此構造函數也被調用了。