我正在为学校进行存储库存计划。我只是不完全了解它，因为我缺乏编程知识，所以我通常只是在youtube上观看视频。如何使“ arraylist对象”可用于以下其他方法？
package ahaprogram2;
import java.util.Scanner;
public class AhaProgram {
public static void main(String[] args) {
Scanner reader = new Scanner (System.in);`
System.out.println("Hello! This is the AHA Program of Jalosjos, Parreno and Alfonso");
System.out.println("Please type the letter of your option");
boolean loop = false;
while (loop != true) {
showOptions();
inputHandler();
String contInput = reader.nextLine();
if (contInput.equals("1")) {
System.out.println("Input the name of Container 1: ");
String ContInp1 = reader.nextLine();
Container container1 = new Container(ContInp1);
container1.printContainer();
}
if (contInput.equals("2")) {
System.out.println("Input the name of Container 2: ");
String ContInp2 = reader.nextLine();
Container container2 = new Container(ContInp2);
container2.printContainer();
}
if (contInput.equals("3")) {
System.out.println("Input the name of Container 3: ");
String ContInp3 = reader.nextLine();
Container container3 = new Container(ContInp3);
container3.printContainer();
}
if (contInput.equals("4")) {
System.out.println("Input the name of Container 4: ");
String ContInp4 = reader.nextLine();
Container container4 = new Container(ContInp4);
container4.printContainer();
}
if (contInput.equals("5")) {
System.out.println("Input the name of Container 5: ");
String ContInp5 = reader.nextLine();
Container container5 = new Container(ContInp5);
container5.printContainer();
}
}
}
public static void showOptions() {
System.out.println("A = Name Containers");
System.out.println("B = Add Cans");
System.out.println("C = Remove Cans");
System.out.println("D = Display Cans");
System.out.println("E = Quit");
System.out.println("Type a Letter: ");
}
public static void inputHandler() {
Scanner reader = new Scanner(System.in);
String input = reader.nextLine();
if(input.equals("A")) {
System.out.println("There are 5 containers.. What container
will you name? ");
System.out.print("Type the number of your container: ");
}
if (input.equals("B")){
System.out.println("Which container will you use?: ");
System.out.print("Type a number for the container: ");
String contforAdd = reader.nextLine();
if (contforAdd.equals("1")) {
System.out.println("How many cans will you add?: ");
int numofCans1 = Integer.parseInt(reader.nextLine());
for (int i = 0; i < numofCans1; i++) {
System.out.print("Enter the name of Can " + (i+1) + " : ");
String CanName = reader.nextLine();
container1.AddCan();
}
}
}
}
}
这里是对象和构造函数的另一类
import java.util.ArrayList;
import java.util.Scanner;
public class Container {
Scanner reader = new Scanner(System.in);
public ArrayList<String> CanContainer = new ArrayList<String>();
public int Contsizep;
public String contName;
public Container(String contname){
this.contName = contname;
}
public void AddCan(String CantoAdd) {
this.CanContainer.add(CantoAdd);
}
public void printContainer() { // for OPTION A ONLY
System.out.println("NAME SUCCESSFUL: **" + contName +"**");
}
}
他们找不到符号“ container1”，因为它没有在范围内声明。.我不知道在范围外声明它
答案 0 :(得分：0)
如果我说对了，请回答您的问题： container1变量的范围在“ main”方法中处于“ if”条件。并且此变量仅在此“ if”条件的括号内可见。如果要将此变量设置为对此类中的其他方法可见，则需要将此变量设置为此类的文件。就您而言，它必须是静态归档的。
public class AhaProgram {
private static Container container1;
public static void main(String[] args) {
Scanner reader = new Scanner (System.in);
System.out.println("Hello! This is the AHA Program of Jalosjos, Parreno and Alfonso");
System.out.println("Please type the letter of your option");
boolean loop = false;
while (loop != true) {
showOptions();
inputHandler();
String contInput = reader.nextLine();
if (contInput.equals("1")) {
System.out.println("Input the name of Container 1: ");
String ContInp1 = reader.nextLine();
container1 = new Container(ContInp1);
container1.printContainer();
}
// ...
}
}
}
答案 1 :(得分：0)
变量的范围表示程序中可访问特定变量的部分（要了解Java变量范围的更多信息，建议阅读this文章）。
关于您的直接关注/问题，您可以在以下if语句中创建变量container1：
if (contInput.equals("1")) {
System.out.println("Input the name of Container 1: ");
String ContInp1 = reader.nextLine();
Container container1 = new Container(ContInp1);
container1.printContainer();
}
这意味着container1的范围或程序中其他方法可以访问它的部分仅限于if语句。您的代码尝试访问函数container1中的inputHandler()，该函数不仅在container1的范围之外，而且在实例化container1之前也被调用。为了使container1可以在if语句之外访问，则必须扩大container1的范围。最好的方法是将其设置为AhaProgram类的静态实例变量。看起来像这样：
public class AhaProgram {
private static Container container1;
public static void main(String[] args) {
Scanner reader = new Scanner (System.in);`
System.out.println("Hello! This is the AHA Program of Jalosjos, Parreno and Alfonso");
System.out.println("Please type the letter of your option");
boolean loop = false;
while (loop != true) {
showOptions();
inputHandler();
String contInput = reader.nextLine();
if (contInput.equals("1")) {
System.out.println("Input the name of Container 1: ");
String ContInp1 = reader.nextLine();
container1 = new Container(ContInp1);
container1.printContainer();
}
// ...the rest of your program...
}
希望这对您有帮助！
答案 2 :(得分：0)
同意jdv的评论。 为了解决该问题，您现在可以将该变量设置为静态字段。
作为临时解决方案，我建议这样做：
import java.util.Scanner;
公共类AhaProgram {
private static Container container;
public static void main(String[] args) {
Scanner reader = new Scanner (System.in);
System.out.println("Hello! This is the AHA Program of Jalosjos,Parreno and Alfonso");
System.out.println("Please type the letter of your option");
boolean loop = false;
while (loop != true)
{
showOptions();
inputHandler();
String contInput = reader.nextLine();
if(contInput.equals("1")) {
System.out.println("Input the name of Container 1: ");
String ContInp1 = reader.nextLine();
container = new Container(ContInp1);
container.printContainer();
}
if (contInput.equals("2")) {
System.out.println("Input the name of Container 2: ");
String ContInp2 = reader.nextLine();
container = new Container(ContInp2);
container.printContainer();
}
if (contInput.equals("3")) {
System.out.println("Input the name of Container 3: ");
String ContInp3 = reader.nextLine();
container = new Container(ContInp3);
container.printContainer();
}
if (contInput.equals("4")) {
System.out.println("Input the name of Container 4: ");
String ContInp4 = reader.nextLine();
container = new Container(ContInp4);
container.printContainer();
}
if (contInput.equals("5")) {
System.out.println("Input the name of Container 5: ");
String ContInp5 = reader.nextLine();
container = new Container(ContInp5);
container.printContainer();
}
}
}
public static void showOptions() {
System.out.println("A = Name Containers");
System.out.println("B = Add Cans");
System.out.println("C = Remove Cans");
System.out.println("D = Display Cans");
System.out.println("E = Quit");
System.out.println("Type a Letter: ");
}
public static void inputHandler() {
Scanner reader = new Scanner(System.in);
String input = reader.nextLine();
if(input.equals("A")){
System.out.println("There are 5 containers.. What container will you name? ");
System.out.print("Type the number of your container: ");
}
if (input.equals("B")){
System.out.println("Which container will you use?: ");
System.out.print("Type a number for the container: ");
String contforAdd = reader.nextLine();
if (contforAdd.equals("1")) {
System.out.println("How many cans will you add?: ");
int numofCans1 = Integer.parseInt(reader.nextLine());
for (int i = 0; i < numofCans1; i++) {
System.out.print("Enter the name of Can " + (i+1) + " :");
String CanName = reader.nextLine();
container.AddCan(CanName);
}
}
}
}
}
希望有帮助！