public class Book{//示例，只是示例
String title;
int pageNum;
int type;
public Book(int pageNum,int type){//这就是传说中的构造方法。
this.title ="计算机";
this.pageNum = pageNum;
this.type = type;
}
}

------解决方案--------------------
Java code
public class Test24 {

    public static void main(String[] args) {
        
        Book book1 = new Book(100, 1);
        book1.detail();
        Book book2 = new Book("java", 200, 2);
        book2.detail();
    }
}

class Book {
    String title;
    int pageNum;
    int type;

    public Book(int pageNum, int type) {
        this.title = "计算机";
        this.pageNum = pageNum;
        this.type = type;
    }
    
    public Book(String title, int pageNum, int type){
        this.title = title;
        this.pageNum = pageNum;
        this.type = type;
    }
    
    public void detail(){
        System.out.println("名称：" + title + ", 页数：" + pageNum + ", 类型：" + type);
    }

}

------解决方案--------------------
public class Book{
   String title;
   int pageNum;
   String type;

public Book(String titile,int pageNum){
   this.title=title;
   this.pageNum=pageNum;
   this.type="计算机";
}

public Book(String titile,int pageNum,String type){
   this.title=title;
   this.pageNum=pageNum;
   this.type=type;
}
}

------解决方案--------------------
不好意思，main方法和detail方法应该写在Book类里面

public String detail(){
     System.out.println(this.title + "---" + this.pageNum + "---" + this.type);
}

public static void main(String[] args){
      Book book1 = new Book("book1",100);
      Book book2 = new Book("book2",200,"文学");
      book1.detail();
      book2.detail();

}