我已经四处寻找这个问题的答案,但到目前为止我还没有理解这一点。我有 3 个 Java 类,BinaryTree 和 HuffmanTree(扩展 BinaryTree)和 HuffmanData(用于 HuffmanTree,与这个问题无关)
HuffmanTree 在其构造函数中显式调用 super()。我无法理解的是为什么它包含对默认构造函数的调用?超类 BinaryTree 根本没有默认构造函数,所以根据我的理解,代码应该抛出异常,但它没有。
这是 BinaryTree 的代码:
public class BinaryTree {
private Comparable data;
private BinaryTree left;
private BinaryTree right;
public final static BinaryTree NIL = new BinaryTree(null, null, null);
// Constructor 1
public BinaryTree (Comparable data, BinaryTree left, BinaryTree right) {
this.data = data;
this.left = left;
this.right = right;
}
// Constructor 2
public BinaryTree (Comparable data) {
this(data, BinaryTree.NIL, BinaryTree.NIL);
}
.
.
. // other methods
}
这是 HuffmanTree 的代码:
public final class HuffmanTree extends BinaryTree implements Comparable {
private String[] table;
private static final int NUM_CHARS = 256;
private static final HuffmanTree NIL = new HuffmanTree();
// Calls default constructor in this class, but how does it work?
// Constructor 1 --- what does this do??
private HuffmanTree() {}
// Constructor 2
private HuffmanTree (char c, int f) {
super(new HuffmanData(c,f), NIL, NIL);
}
// Constructor 3
private HuffmanTree (HuffmanTree left, HuffmanTree right) {
super(new HuffmanData( (char)0, left.frequency()+right.frequency()),
left, right);
}
.
.
. // other methods
}
如果问题不清楚,请道歉。请让我知道如何更好地解释它。