java  List循环与Map循环的总结

   @Test 
public void ForListTest() { 
  List<String> list = new ArrayList<String>(); 
  list.add("1"); 
  list.add("2"); 
  list.add("3"); 
  list.add("4"); 
  list.add("5"); 
 
  // 迭代器循环不需要知道集合的大小以及类型，最佳选择 
  for (@SuppressWarnings("rawtypes") 
  Iterator iterator = list.iterator(); iterator.hasNext();) { 
    String list = (String) iterator.next(); 
    System.out.println("01)Iterator for：===============" + list); 
  } 
 
  // foreach相对比for来讲，不需要知道集合的长度 
  for (String list : list) { 
    System.out.println("02)foreach:=================" + list); 
  } 
 
  // for循环既需要知道集合的大小，而且要求是有序的 
  for (int i = 0; i < list.size(); i++) { 
    System.out.println("03)for==================" + list.get(i)); 
  } 
} 

   @Test 
public void ForMapTest() { 
  Map<String, String> map = new HashMap<String, String>(); 
  map.put("01", "1"); 
  map.put("02", "2"); 
  map.put("03", "3"); 
  map.put("04", "4"); 
  map.put("05", "5"); 
  Set<String> keySet = map.keySet(); 
  //1.keyset的foreach方法 
  for (String key : keySet) { 
    System.out.println("1)keyset:" + "key:" + key + " value:" 
        + map.get(key)); 
  } 
 
  Set<Entry<String, String>> entrySet = map.entrySet(); 
  //2.entryset的迭代方法 
  for (@SuppressWarnings("rawtypes") 
  Iterator iterator = entrySet.iterator(); iterator.hasNext();) { 
    @SuppressWarnings("unchecked") 
    Entry<String, String> entry = (Entry<String, String>) iterator 
        .next(); 
    System.out.println("02)entrySet,iterator: key:" + entry.getKey() 
        + " value:" + entry.getValue()); 
  } 
 
  //3.推荐，容量最大 
  for (Entry<String, String> entry : entrySet) { 
    System.out.println("03)entrySet,foreach:key:" + entry.getKey() 
        + " value:" + entry.getValue()); 
  } 
 
  Collection<String> values = map.values(); 
  //4.只循环出value的方法 
  for (String value : values) { 
    System.out.println("04)values,just for values,value:" + value); 
  } 
 
}