如何使用List对象实现去重

public class People {    private int id;   private String name;   private Date createDate;    public int getId() {     return id;   }    public void setId(int id) {     this.id = id;   }    public String getName() {     return name;   }    public void setName(String name) {     this.name = name;   }    public Date getCreateDate() {     return createDate;   }    public void setCreateDate(Date createDate) {     this.createDate = createDate;   }  }