刚看到设计桟类的部分，问题：
1 package helloworld;
2 public class StackOfIntegers {
3 private int[] elements;
4 private int size;
5 public static final int DEFAULT_CAPACITY = 16;
6 public StackOfIntegers(){
7 this (DEFAULT_CAPACITY);
8 }
9 public StackOfIntegers(int capacity){
10 elements = new int[capacity];
11 }
12 public void push(int value){
13 if(size >= elements.length){
14 int[] temp = new int[elements.length * 2];
15 System.arraycopy(elements, 0, temp, 0, elements.length);
16 elements = temp;
17 }
18 elements[size++] = value;
19 }
20 public int pop(){
21 return elements[--size];
22 }
23 public int peek(){
24 return elements[size - 1];
25 }
26 public boolean empty(){
27 return size == 0;
28 }
29 public int getSize(){
30 return size;
31 }
32 }
请问第6-8行这个
6 public StackOfIntegers(){
7 this (DEFAULT_CAPACITY);
8 }
到底啥意思？？一直搞不懂
还有26-28行这个
26 public boolean empty(){
27 return size == 0;
28 }
啥意思？？
谢大神了