过去几天我一直在创建一个简单的图书馆系统，由于这个网站，我已经完成了每个架子，显示等的人口。目前，我遇到了借款人借用实体书，下载电子书或借用设备的问题。首先，运行时出现零点异常错误，调用borrowBookPH时出错，最后，我不知道该书是否真正被借用或下载。
我发布了一个缩短的图书馆计划代码。
编辑：我已经设法弄清楚是什么导致了我的问题。现在我的问题是当我被问到“输入书/设备名称：”时，我无法输入任何字符串。我的代码上没有错误/警告。
驱动程序类：
System.out.println("Input Borrower: ");
int borrowerID = sc.nextInt();
switch(borrowerID){
case 11074450: System.out.println("1. Physical 2. Digital 3. Equipment: ");
int choice = sc.nextInt();
switch(choice){
case 1: System.out.println("Input Book Name: ");
String borrowIP = sc.nextLine();
for(int i = 0; i < ph.size(); i++){
if(borrowIP.equals(ph.get(i).getTitle()))
brw1.borrowBookPH(ph.get(i));
}
break;
case 2: System.out.println("Input Book Name: ");
String borrowID = sc.nextLine();
for(int i = 0; i < dg.size(); i++){
if(borrowID.equals(dg.get(i).getTitle()))
brw1.downloadBookDG(dg.get(i));
}
break;
case 3: System.out.println("Input Equipment Name: ");
String borrowIE = sc.nextLine();
for(int i = 0; i < eqp.size(); i++){
if(borrowIE.equals(eqp.get(i).getName()))
brw1.borrowEQ(eqp.get(i));
}
break;
}
break;
case 10355230: System.out.println("1. Physical 2. Digital 3. Equipment: ");
int choice2 = sc.nextInt();
switch(choice2){
case 1: System.out.println("Input Book Name: ");
String borrowIP = sc.nextLine();
for(int i = 0; i < ph.size(); i++){
if(borrowIP.equals(ph.get(i).getTitle()))
brw2.borrowBookPH(ph.get(i));
}
break;
case 2: System.out.println("Input Book Name: ");
String borrowID = sc.nextLine();
for(int i = 0; i < dg.size(); i++){
if(borrowID.equals(dg.get(i).getTitle()))
brw2.downloadBookDG(dg.get(i));
}
break;
case 3: System.out.println("Input Equipment Name: ");
String borrowIE = sc.nextLine();
for(int i = 0; i < eqp.size(); i++){
if(borrowIE.equals(eqp.get(i).getName()))
brw2.borrowEQ(eqp.get(i));
}
break;
}
break;
case 11423970: System.out.println("1. Physical 2. Digital 3. Equipment: ");
int choice3 = sc.nextInt();
switch(choice3){
case 1: System.out.println("Input Book Name: ");
String borrowIP = sc.nextLine();
for(int i = 0; i < ph.size(); i++){
if(borrowIP.equals(ph.get(i).getTitle()))
brw3.borrowBookPH(ph.get(i));
}
break;
case 2: System.out.println("Input Book Name: ");
String borrowID = sc.nextLine();
for(int i = 0; i < dg.size(); i++){
if(borrowID.equals(dg.get(i).getTitle()))
brw3.downloadBookDG(dg.get(i));
}
break;
case 3: System.out.println("Input Equipment Name: ");
String borrowIE = sc.nextLine();
for(int i = 0; i < eqp.size(); i++){
if(borrowIE.equals(eqp.get(i).getName()))
brw3.borrowEQ(eqp.get(i));
}
break;
}
break;
case 11092001: System.out.println("1. Physical 2. Digital 3. Equipment: ");
int choice4 = sc.nextInt();
switch(choice4){
case 1: System.out.println("Input Book Name: ");
String borrowIP = sc.nextLine();
for(int i = 0; i < ph.size(); i++){
if(borrowIP.equals(ph.get(i).getTitle()))
brw4.borrowBookPH(ph.get(i));
}
break;
case 2: System.out.println("Input Book Name: ");
String borrowID = sc.nextLine();
for(int i = 0; i < dg.size(); i++){
if(borrowID.equals(dg.get(i).getTitle()))
brw4.downloadBookDG(dg.get(i));
}
break;
case 3: System.out.println("Input Equipment Name: ");
String borrowIE = sc.nextLine();
for(int i = 0; i < eqp.size(); i++){
if(borrowIE.equals(eqp.get(i).getName()))
brw4.borrowEQ(eqp.get(i));
}
break;
}
break;
case 10911550: System.out.println("1. Physical 2. Digital 3. Equipment: ");
int choice5 = sc.nextInt();
switch(choice5){
case 1: System.out.println("Input Book Name: ");
String borrowIP = sc.nextLine();
for(int i = 0; i < ph.size(); i++){
if(borrowIP.equals(ph.get(i).getTitle()))
brw5.borrowBookPH(ph.get(i));
}
break;
case 2: System.out.println("Input Book Name: ");
String borrowID = sc.nextLine();
for(int i = 0; i < dg.size(); i++){
if(borrowID.equals(dg.get(i).getTitle()))
brw5.downloadBookDG(dg.get(i));
}
break;
case 3: System.out.println("Input Equipment Name: ");
String borrowIE = sc.nextLine();
for(int i = 0; i < eqp.size(); i++){
if(borrowIE.equals(eqp.get(i).getName()))
brw5.borrowEQ(eqp.get(i));
}
break;
}
break;
}
借款人类：
private Physical borrowedP;
private Digital borrowedD;
private Equipment borrowedE;
public void borrowBookPH(Physical borrow){
this.borrowedP = borrow;
this.borrowedP.borrowPH(this);
public void downloadBookDG(Digital borrow){
this.borrowedD = borrow;
this.borrowedD.borrowDG(this);
this.borrowedD.countDownload();
}
public void borrowEQ(Equipment borrow){
this.borrowedE = borrow;
this.borrowedE.borrowEQ(this);
}
物理等级：
public void borrowPH(Borrower borrower){
this.isAvailable = false;
this.borrower = borrower;
}
public void returnPH(){
this.isAvailable = true;
this.borrower = null;
}
数字课程：
public void countDownload(){
this.count += 1;
}
public void showDownload(){
System.out.println(this.count);
}
public void borrowDG(Borrower borrower){
this.status = false;
this.borrower = borrower;
countDownload();
}
设备类：
public void borrowEQ(Borrower borrower){
this.isAvailable = false;
this.borrower = borrower;
}
乎乎。请帮忙。这个'我不能打字'令人沮丧。
答案 0 :(得分：0)
至于错误，你的代码似乎缺少一些try {} catche（）{}和测试（物理借用，还是我可以把它交给某人？）。你的代码也缺少了inicialization部分，这也可能有问题。
对于方法中的错误，请尝试跟踪它，或者使用相应的代码发布e.printStackTrace（）。
借用或下载不应该是一个问题，你将它们放在不同的类中并且命名不同，那么你究竟是什么意思“我不知道这本书是真的被借用还是下载了”