1.遍历List，ArrayList

public static void print(List
     
       list) {      Iterator
      
        itr = list.iterator();      while (itr.hasNext()) {          System.out.print(itr.next());          System.out.print(", ");      }      System.out.println();  }
      
     

List

2.遍历Map

public static void main(String[] args) {  Map
     
       map = new HashMap
      
       ();  map.put("1", "value1");  map.put("2", "value2");  map.put("3", "value3");   //第一种：普遍使用，二次取值  System.out.println("通过Map.keySet遍历key和value：");  for (String key : map.keySet()) {   System.out.println("key= "+ key + " and value= " + map.get(key));  }   //第二种  System.out.println("通过Map.entrySet使用iterator遍历key和value：");  Iterator
       
        
         > it = map.entrySet().iterator();  while (it.hasNext()) {   Map.Entry
         
           entry = it.next();   System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());  }                                                               //第三种：推荐，尤其是容量大时  System.out.println("通过Map.entrySet遍历key和value");  for (Map.Entry
          
            entry : map.entrySet()) { System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue()); } //第四种 System.out.println("通过Map.values()遍历所有的value，但不能遍历key"); for (String v : map.values()) { System.out.println("value= " + v); } }
          
         
        
       
      
     

private static void visitMapByKey(Map map) {        Iterator keys = map.keySet().iterator();        while(keys.hasNext()){            Object key = keys.next();//key            Object value = map.get(key);//上面key对应的value        }    }

3.去重

public static ArrayList
     
       removeDuplicateWithOrder(ArrayList
      
        contancts)    {        HashSet
       
         hashSet = new HashSet
        
         ();        ArrayList
         
           newlist = new ArrayList
          
           (); for (Iterator
           
             iterator = contancts.iterator(); iterator.hasNext();) { PocContactModel element = (PocContactModel) iterator.next(); if (hashSet.add(element)) { newlist.add(element.getSipUri()); } } contancts.clear(); return newlist; }