Map、ArrayList 的遍历

public static void main(String[] args) {
  Map<String, String> couples = new HashMap<String, String>();
  couples.put("郭靖", "黄容");
  couples.put("乔峰", "阿朱");
  couples.put("杨过", "小龙女");
  couples.put("胡斐", "苗若兰");

  System.out.println(couples);
  
  System.out.println("使用映射项遍历Map:");
  Set<Map.Entry<String, String>> entrySet = couples.entrySet();
  for (Map.Entry<String, String> entry : entrySet) {
   System.out.println(entry.getKey() + " : " + entry.getValue());
  }
  
  System.out.println("使用Key遍历Map:");
  Set<String> keySet = couples.keySet();
  for (String key : keySet) {
   System.out.println(key + " : " + couples.get(key));
  }
  
  ArrayList<String> actors = new ArrayList<String>();
  actors.ensureCapacity(50);
  actors.add("郭靖");
  actors.add("黄容");
  actors.add("乔峰");
  actors.add("阿朱");
  actors.trimToSize();
  
  System.out.println("Index遍历:");
  for(int i=0;i<actors.size();i++){
   System.out.println(actors.get(i));
  }
  
  System.out.println("迭代器遍历:");
  for(Iterator<String> it = actors.iterator();it.hasNext();){
   System.out.println(it.next());
  }
  
  System.out.println("For-Each遍历:");
  for(String actor:actors){
   System.out.println(actor);
  }
 }