import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;

public class ThreePrint {

public static void main(String[] args) {
List<String> list = new ArrayList<String>();
list.add("aaa");
list.add("bbb");
list.add("ccc");

//普通for迴圈，通過.get()來獲取每個位置的下標
for (int i = 0; i < list.size(); i++) {
System.out.print(list.get(i)+" ");
}

//增強for迴圈，s為變數，直接列印即可
for (String s : list) {
System.out.print(s+" ");
}

//Iterator ，單向迭代器 it.hasNext()指向下一個指標，it.next()指向下一個數
Iterator<String> it = list.iterator();
while (it.hasNext()) {
String s = it.next();
System.out.print(s+" ");
}

//繼承了Iterator迭代器，功能更加強大，是雙向的，可以逆序列印。

正序列印集合
ListIterator<String> lit = list.listIterator();
while (lit.hasNext()) {
String s = lit.next();
System.out.print(s+" ");
}

//逆序列印集合

while (lit.hasPrevious()) {
String s = lit.previous();
System.out.print(s+" ");
}

}

}