借书系统，首先创建了一个父类books：
public class books {
int sequence;//属性，序列号
String name;//属性，名称
public books(int sequence, String name) {
// TODO Auto-generated constructor stub
this.name = name;//赋值，以便后面主函数调用
this.sequence=sequence;
}
}

创建子类SerialNumberQuery：
import java.util.Scanner;
public class SerialNumberQuery {
public void SerialNumberQuery(int sequence,String name,books[] bb){
SerialNumberQuery tet=new SerialNumberQuery();
Scanner Qz=new Scanner(System.in);
try {
System.out.println("请输入要查找的书籍序列号：");
int c=Qz.nextInt();
int x=bb[c-1].sequence;
if(c==x){
System.out.println("您借阅的书籍是："+bb[c-1].name+"\t欢迎再次借阅!");
}} catch (Exception e){
System.out.println("您输入有误或者不存在，请重新输入！");
tet.SerialNumberQuery(sequence, name, bb);
}

    }

}

创建一个子类NameQuery：
import java.util.InputMismatchException;
import java.util.Scanner;
public class NameQuery {
public void NameQuery(int sequence,String name,books[] bb){

    NameQuery tet1=new NameQuery();
    Scanner Qz=new Scanner(System.in);
    try {
        System.out.println("请输入要查找的书籍的书名：");
        String c=Qz.next();
        int i;
        for( i=0;i<bb.length;i++){  
            //System.out.println(bb[i]);
             if(c.equals(bb[i].name)){
                  break;}
        } 
         System.out.println("您借阅的书籍是："+bb[i].name+"\t欢迎再次借阅!");
        } catch (Exception e){
                System.out.println("您输入有误或者不存在，请重新输入！");
                tet1.NameQuery(sequence, name, bb);

        }

}
}
主函数function:
import java.util.Scanner;
public class function {
private static int sequence;
private static String name;
static books[] bb={new books(1,"高数"),
new books(2,"论语"),
new books(3,"英语")
};

public static void main(String[] args) {
    Scanner Qz=new Scanner(System.in);
    // TODO Auto-generated method stub
    SerialNumberQuery tet=new SerialNumberQuery();
    NameQuery tet1=new NameQuery();
    System.out.println("*****请问您是否需要查阅书籍？*****");
    System.out.println("是请输入1\t否请输入0");
    int a=Qz.nextInt();
    if(a==1){
    System.out.println("按序列查找请按1：");
    System.out.println("按书名查找请按0：");
    int b=Qz.nextInt();
    switch (b) {
    case 1:
        tet.SerialNumberQuery(sequence, name, bb);

        break;
    case 0:
        tet1.NameQuery(sequence, name, bb);
        break;

    }

        System.out.println("欢迎下次再来！！！");
    }
    else{
        System.out.println("欢迎下次再来！！！");
    }
}

}