麻烦老师看下哪边有问题，私有属性该如何赋值呢，

public class Book {
  //私有属性：书名、作者、出版社、价格
  public Book(){
  }
  private String bookName;
  private String writer;
  private String publisher;
  private double price;
  //通过构造方法实现属性赋值
  public String getBookName(){
      return "书名:"+bookName;
  }
  public String getWriter(){
      return "作者："+writer;
  }
  public void setPublisher(String publisher){
      this.publisher=publisher;
  }
  public String getPublisher(){
      return "出版社:"+this.publisher;
  }
  public void setPrice(double price){
      if(price<=10){
          System.out.print("此价格低于成本价,以成本价出售：");
          this.price=10;
          System.out.println();
          }else{
              this.price=price;
          }
  }
   public double getPrice(){
      return "价格:"+this.price+"元";
  }