是什么导致我的while循环脱轨？

Question

Alright, so I have a while loop that is made to execute while the length of a string is 0, and when the string is initialized as an empty string it works just fine for the first pass, but after completing the rest of the loop that this loop is nested in, it just breaks and works in a completely unintended manner. Could somebody examine this for me and help me figure out whats wrong?

import java.util.*;
public class Project5
{
   public static void main(String[] args)
   {
       List namesLinkedList = new LinkedList();//creates a new linked list called namesLinkedList
       List ageLinkedList = new LinkedList();//creates a new linked list called ageLinkedList
       List salaryLinkedList = new LinkedList();//creates a new linked list called salaryLinkedList
       int length = loadLists(namesLinkedList, ageLinkedList, salaryLinkedList);//
       printLists(namesLinkedList, ageLinkedList, salaryLinkedList,length);
   }


    public static int loadLists(List namesLinkedList, List ageLinkedList, List salaryLinkedList)
    {
        Scanner input = new Scanner(System.in);
        String check1 = new String();
        int check2 = 0;
        int check3 = 0;
        String name = new String();
        int age = 0;
        int salary = 0;
        int count = 0;
        while(check1 != "9999")
       {
          while(name.equals(""))
          {

               System.out.print("Please enter an employee name: ");
               name = input.nextLine().trim();
               if(name.length() == 0)
               {
                 System.out.println("An employees name can't be an empty string."); 
               }
               else
               {
                   check1 = name;
               }
            }

           if(check1.equals("9999"))
           {
            break;   
           }

           while(check2 > 68 || check2 < 23)
           {
               System.out.print("Please enter an age for this employee: ");
               age = input.nextInt();
               if(age > 68 || age < 23)
               {
                   System.out.println("This age is not within the allowed range.( 23-68)");
               }
               else
               {
                   check2 = age;
               }
           }

           while(check3 > 120000 || check3 < 30000)
           {
               System.out.print("Please enter a salary for this employee: ");
               salary = input.nextInt();
               if(salary > 120000 || salary < 30000)
               {
                   System.out.println("This salary is not within the allowed range(30000-120000).");
               }
               else
               {
                   check3 = salary;
               }
           }
           namesLinkedList.add(name);
           ageLinkedList.add(age);
           salaryLinkedList.add(salary);
           check1 = "";
           name = "";
           age = 0;
           salary = 0;
           count++;
       }
        return count;
    }

    public static void printLists(List namesLinkedList, List ageLinkedList, List salaryLinkedList, int listLength)
    {
        System.out.printf("%-20s %-20s %14s\n", "Name","Age", "Salary");//prints a header
        for(int i = 0; i < listLength; i++)
        {
           System.out.printf("%-20s %-20s %14s\n", namesLinkedList.get(i),ageLinkedList.get(i),salaryLinkedList.get(i));
        }
    }
}

and the output ends up being something like this:

Please enter an employee name: Ace
Please enter an age for this employee: 12
This age is not within the allowed range.( 23-68)
Please enter an age for this employee: 34
Please enter a salary for this employee: 12000
This salary is not within the allowed range(30000-120000).
Please enter a salary for this employee: 45000
Please enter an employee name: An employees name can't be an empty string.
Please enter an employee name: Ellie
Please enter an employee name: Elise
Please enter an employee name: Alan
Please enter an employee name: 9999
Name                 Age                          Salary
Ace                  34                            45000
Ellier               0                                 0
Elise                0                                 0
Alan                 0                                 0

As shown here, the loop fails to execute properly any time after the first. It's as if the name.length() value isnt properly resetting

Answer 1

While (!check1.equals("9999"));

at the end while reseting values, reset check2 and check3

 check1 = "";
       name = "";
       check2=0;
       check3=0;
       age = 0;
       salary = 0;
       count++;

Answer 2

I'm going to go ahead and say it's because you aren't resetting your other check variables ( check2 and check3 ).

Consequently, the same check values will be used in your loop, but you still reset age and salary on each loop.

First loop
    Name loop
        check1 assigned as name is validation passes
    Age
        check2 assigned age if in range
    Salary
        check3 assigned if salary in range
    check1 = 0
    age = 0
    salary = 0
    check2 and check3 still equal previous age and salary
    leaving them valid values
Second loop
    Name loop
        check1 assigned (validation passing of course)
    Age loop
        check2 already assigned in range, next
    Salary loop
        check3 already assigned in range, next
Rinse, Repeat

Since you don't seem to want to listen to reason, I compiled this in Netbeans and output check2 and check3 after each iteration. Perhaps this will show you that this is your issue:

run:
Please enter an employee name: Ted
check2 currently equals 0
Please enter an age for this employee: 45
check3 currently equals 0
Please enter a salary for this employee: 67000
Please enter an employee name: An employees name can't be an empty string.
Please enter an employee name: Fred
check2 currently equals 45
check3 currently equals 67000
Please enter an employee name: Jane
check2 currently equals 45
check3 currently equals 67000
Please enter an employee name: Perry
check2 currently equals 45
check3 currently equals 67000
Please enter an employee name: 

Answer 3

== tests for reference equality.

.equals() tests for value equality.

== worked in C#