我正在创建一本图书库存计划。
我有两个类,一个是主类,另一个是构造函数类名Item
。
在主类上,我创建了一个数组(Item[] book = new Item[100])
来存储我的输入。
在我的Item
课程中,我想在
public boolean addItem(Item[] iArray, String itemCode){
boolean c = false;
for(int i=0; i<iArray.length; i++){
if(iArray[i].getItemCode().equals(itemCode)){
c = true;
}
else{
c = false;
}
}
return c;
}
如何让Item[] iArray
与主要类中的书籍数组同步?
public class Item {
private String itemCode;
private String description;
private int quantity;
private double costprice;
private double sellprice;
private String status = "Available";
private boolean check;
private double discount;
public Item(){
this("A000","default",0,0.00,0.00,0.25,"Available");
}
//construtor with parameter
public Item(String itemCode, String description, int quantity, double costprice, double sellprice, double discount, String status){
this.setItemCode(itemCode);
this.setDescription(description);
this.setQuantity(quantity);
this.setCostprice(costprice);
this.setSellprice(sellprice);
this.setStatus(status);
this.setDiscount(discount);
}
//setter and getter methods
public void setItemCode(String itemCode){
this.itemCode = itemCode;
}
public String getItemCode(){
return this.itemCode;
}
public void setDescription(String description){
this.description = description;
}
public String getDescription(){
return this.description;
}
public void setQuantity(int quantity){
this.quantity = quantity;
}
public int getQuantity(){
return this.quantity;
}
public void setCostprice(double costprice){
this.costprice = costprice;
}
public double getCostprice(){
return this.costprice;
}
public void setSellprice(double sellprice){
this.sellprice = sellprice;
}
public double getSellprice(){
return this.sellprice;
}
public void setStatus(String status){
this.status = status;
}
public String getStatus(){
return this.status;
}
public void setDiscount(double discount){
this.discount = discount;
}
public double getDiscount(){
return this.discount;
}
public void setCheck(boolean check){
this.check = check;
}
public boolean getCheck(){
return this.check;
}
public boolean addItem(Item[] iArray, String itemCode){
boolean c = false;
for(int i=0; i<iArray.length; i++){
if(iArray[i].getItemCode().equals(itemCode)){
c = true;
}
else{
c = false;
numberofobject++;
}
}
return c;
}
public void displaymenu(){
System.out.println("Menu");
System.out.println("1. Add New Item");
System.out.println("2. Search");
System.out.println("3. Edit Details");
System.out.println("4. Edit Quantity");
System.out.println("5. Stop Sell");
System.out.println("6. List");
System.out.println("7. Exit");
}*/
public String toString(){
String msg = "";
msg = this.getItemCode()+"\t\t\t\t"+this.getDescription()+"\t\t\t\t"+this.getQuantity()+"\t\t\t\t"+this.getCostprice()+"\t\t\t\t"+this.getSellprice()+"\t\t\t\t"+this.getDiscount()+"\t\t\t\t"+this.getStatus();
return msg;
}
这是我的Item类。
import java.util.*;
public class Driver {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
int choice,quantity,NOI=0;
double cprice,sprice,discount;
String itc,name,status = "Available";
boolean check = true;
Item[] book = new Item[100];
Scanner s1 = new Scanner(System.in);
do{
Item display = new Item();
display.displaymenu();
System.out.print("Please Select Menu: ");
choice = s1.nextInt();
if(choice==1){
do{
System.out.print("Please Enter the Item Code: ");
itc = s1.next();
//for(int i=0; i<book.length; i++){
//book[i].addItem(book, itc);
if(display.addItem(book, itc)==true){
System.out.println("the book item code already exist."+NOI);
check = false;
}
else
{
check = true;
} //This is the question where i faced.
//}
}while(check==false);
System.out.print("Please Enter the Description: ");
name = s1.next();
System.out.print("Please Enter the Quantity: ");
quantity = s1.nextInt();
System.out.print("Please Enter the Cost Price: ");
cprice = s1.nextDouble();
System.out.print("Please Enter the Sell Price: ");
sprice = s1.nextDouble();
System.out.print("Please Enter the Discount: ");
discount = s1.nextDouble();*/
book[NOI] = new Item(itc,name,quantity,cprice,sprice,discount,status);
NOI++;
}
当我添加第二个项目时,出现错误(线程“main”java.lang.NullPointerException中的异常),
如何解决?
答案 0 :(得分:1)
您的方法无法执行您想要的操作,因为即使找到项目代码,循环也会继续。你可能想要这样的东西:
public boolean addItem(Item[] iArray, String itemCode){
for (Item item : iArray) {
if (item.getItemCode().equals(itemCode)) {
return true;
}
}
return false;
}
请注意,您发布的方法看起来很奇怪,因为它不会在任何地方添加任何内容。
您也可以考虑使用List<Item>
(ArrayList
等)代替Item[]
。
答案 1 :(得分:0)
我不确定我理解你在寻找什么,所以如果我的答案无关紧要,只需评论它,我就会删除。
我假设您正在尝试存储信息:将新项目及其代码添加到数组中。但我不确定你是不是:
在插入之前尝试确保项目在数组中的唯一性:
也许您可以使用一组代码,它会简化您的问题,只需检查.contains()然后添加或不添加
尝试将其添加到列表中,如果已经存在则执行某些操作(增加代码的书数?)
也许您可以使用HashMap将代码作为密钥并预订为项目。
在您当前的状态下,您的方法addItem不会添加任何内容,只需返回数组中的最后一本书与您的代码匹配...