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);   }  }