###问题描述：

###原来

List
    
      result = Lists.newArrayList();Iterator
     
       iterator = source.iterator();String current = null;while (iterator.hasNext()) {    if (current == null) {        current = iterator.next();    }    result.add(current);    while (iterator.hasNext()) {        String next = iterator.next();        if (current.equals(next)) {            continue;        }        current = next;        break;    }}if (current != null && !result.get(result.size() - 1).equals(current)) {    result.add(current);}
     
    

因为需要在下一个元素与当前元素不相等的时候保留上一个元素，所以写起来比较复杂用了两层循环，并且容易写错，改了好几遍才通过测试用例

###使用Guava

List
    
      result = Lists.newArrayList();PeekingIterator
     
       iterator = Iterators.peekingIterator(source.iterator());String current = null;while (iterator.hasNext()) {    if (!iterator.peek().equals(current)) {        current = iterator.next();        result.add(current);    } else {        iterator.next();    }}
     
    

使用PeekingIterator，代码精简许多，也更易于理解，也不容易写错