去除arraylist容器中的相同的对象元素的方法

<span class="keyword" style="background-color: rgb(250, 250, 250); font-size: 1em; font-family: Monaco, 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', Consolas, 'Courier New', monospace;">boolean</span><span style="color: black; background-color: rgb(250, 250, 250); font-size: 1em; font-family: Monaco, 'DejaVu Sans Mono', 'Bitstream Vera Sans Mono', Consolas, 'Courier New', monospace;"> retainAll(Collection<?> c); </span>

<pre name="code" class="html">List<Employee> <span style="font-family: Arial, Helvetica, sans-serif;">employeeOfIntermediarys </span><span style="font-family: Arial, Helvetica, sans-serif;">= new ArrayList<Employee>();</span><pre name="code" class="html">List<Employee> <span style="font-family: Arial, Helvetica, sans-serif;">tempList </span><span style="font-family: Arial, Helvetica, sans-serif;">= new ArrayList<Employee>();</span>

if(tempList != null){<span style="white-space:pre">	</span>//去掉<span style="font-family: Arial, Helvetica, sans-serif;">tempList 中与</span><span style="font-family: Arial, Helvetica, sans-serif;">employeeOfIntermediarys 中</span>相同的元素，在合并	List<Employee> eoiList = new ArrayList<Employee>(employeeOfIntermediarys);	if (eoiList.retainAll(tempList)) {		tempList.removeAll(eoiList);	}

	employeeOfIntermediarys.addAll(tempList);}

public class Book {	private int id;	private String nameString;	private String writer;		public Book(){		id= -1;		nameString = "";		writer = "";	}

List<Book> books = new ArrayList<Book>();  List<Book> tempList = new ArrayList<Book>();    Book book1 = new Book();  book1.setId(1);  book1.setNameString("dkjdf");    Book book2 = new Book();  book2.setId(2);  book2.setNameString("到加福禄寿");    Book book3 = new Book();  book3.setId(3);  book3.setNameString("dj地方");    Book book4 = new Book();  book4.setId(4);  book4.setNameString("dkjdf");    Book book5 = new Book();  book5.setId(5);  book5.setNameString("到加福禄寿");    Book book6 = new Book();  book6.setId(6);  book6.setNameString("dj地方");      books.add(book1);  books.add(book2);  books.add(book5);  books.add(null);    tempList.add(book1);  tempList.add(book4);  tempList.add(null);  tempList.retainAll(books);  System.out.println(tempList.get(0).booktoString());

	@Override	public boolean equals(Object c){		if (!(c instanceof Employee)) {			return false;		}		Employee eoi = (Employee) c;		if (eoi.getUserGuid().equals(userGuid)) {			return true;		}		return false;			}