循环我有这样的代码,涉及任务做的ArrayList
names
,其包括像添加元素在ArrayList
,显示ArrayList
的元素,在一ArrayList
删除的元素,在ArrayList
编辑元件功能。与ArrayList的
我的问题是当我在ArrayList
中添加一个新名称,当代码循环回来并且我想查看ArrayList
中的元素时,它变为空白。
import java.util.ArrayList;
import java.util.Scanner;
public class mainRunner {
public static void main(String[] args) {
String con;
do {
menuCaller();
System.out.println("Do you want to continue[Y/N]");
Scanner confirm = new Scanner(System.in);
con = confirm.nextLine();
} while (con.equalsIgnoreCase("y"));
}
public static void menuCaller() {
int choice;
ArrayList names = new ArrayList();
int firstIndex =0;
Scanner scan = new Scanner(System.in);
Scanner scan2 = new Scanner(System.in);
Scanner scaned = new Scanner(System.in);
System.out.println("Menu"
+"\n[1] Add Name"
+ "\n[2] Display All Record"
+ "\n[3] Delete a Record"
+ "\n[4] Edit a R1ecord "
+ "\n[5] Exit");
choice = scaned.nextInt();
if (choice == 1) {
System.out.println("***ADDING NAMES***");
System.out.println("Enter the name of the Student");
String addName = scan.next();
names.add(addName);
System.out.println("Record Added !!!");
}
else if (choice == 2) {
System.out.println("***Database Content**");
System.out.println("------------------------");
System.out.println("Record # | Name ");
for (int index = firstIndex; index < names.size(); ++index) {
System.out.println("--------------------");
System.out.println(" " + index + " | " +names.get(index));
}
}
else if (choice == 3) {
System.out.println("***Delete A Record***");
System.out.print("Enter a number to be deleted: ");
int numDelete = scan.nextInt();
names.remove(numDelete);
System.out.println("Record Deleted");
}
else if (choice == 4) {
System.out.println("***Edit Record***");
System.out.println("***Database Content**");
System.out.println("------------------------");
System.out.println("Record # | Name ");
for (int index = firstIndex; index < names.size(); ++index) {
System.out.println("--------------------");
System.out.println(" " + index + " | " +names.get(index));
}
System.out.println("Enter the Name to be Edited");
String nameEdited = scan.next();
if (names.indexOf(nameEdited) >= 0) {
System.out.print("Change to: ");
String nameChange = scan2.next();
names.set(names.indexOf(nameEdited), nameChange);
}
else {
System.out.println("Record Not Existing");
}
}
else if (choice == 5) {
System.out.println("Thank you for using the Program");
System.exit(choice);
}
else {
System.out.println("Wrong Choice");
}
}
}
在'menuCaller()'你始终创建的'names'一个新的(空)名单。 – Marvin
为什么每次你想要从System.in读取数据时都要创建新的扫描仪?创建一个并重用它。 – Pshemo