Replacing an Element

Question

I'm working on code that shows the simple operation of an array. I can't seem to make it work at the part of re-inserting a deleted element inside my created array. My goal is to put another element inside another deleted element (when I delete an element it becomes 0). My insert case just tells the duplicate input, it does not let me resume in the deleted element at a certain position.

          case 2:
         {
          if (limit1 < 5 || limit1 > 20){
            System.out.println("Error: Invalid Array Limit");
            System.out.println("Press Any Key To Continue...");
            new java.util.Scanner(System.in).nextLine();
            System.out.print('\u000C');
            m();
            }
            else{
            System.out.println("Enter the " + array.length + " numbers now. 
            Or enter -1 to exit");
            int i = 0;
            while(i < array.length){
               array[i] = in.nextInt();
               boolean dups = false;    
             if(array[i] != -1){
             for(int k = 0; k < i; k++)
                if(array[k] == array[i])
                {
                    System.out.println("Error: Duplicate Element");
                    System.out.println("Please Enter Another Value");
                    dups = true;
                    break;
                }
                if(!dups){
                i++;}
           }
           else{
               array[i] = 0;
               System.out.println("Exit Confirmed");
               System.out.println("Press Any Key To Continue...");
               new java.util.Scanner(System.in).nextLine();
               System.out.print('\u000C');
               m();
            }
        }
          System.out.println("You have entered the "+ limit1 + " numbers");
          System.out.println("Press Any Key To Continue...");
          new java.util.Scanner(System.in).nextLine();
          System.out.print('\u000C');
          m();
          } 
        } 

Another problem is, if I input a sentinel value (-1), it just makes the current input position 0. I just wish to exit the case not put a 0 at the position

Answer 1

I see some problems with your code. Using switch statements without any break statements is not a good practice. You can easily refactor your method to use a while loop like this:

public void e() {
    do {
        m();
        choice1 = in.nextInt();

        cls();
        if (choice1 > 0) {
            processChoice(); // contains switch block for processing input
        }
    } while (choice1 > 0); // Loop will terminate when user presses 0
}

This should also exit your program whenever user presses 0.

I see a problem in your Insertion into array block. You seem to be assigning value received from input directly to array[i]. What's the point of checking if it's a duplicate value after assigning it to array[i]. I think you should do something like this:

while (i < array.length) {
    int currentInput = in.nextInt();
    boolean dups = false;
    if (array[i] != -1) {
        for (int k = 0; k < i; k++)
            if (array[k] == currentInput) {
                System.out.println("Error: Duplicate Element");
                System.out.println("Please Enter Another Value");
                dups = true;
                break;
            }
        if (!dups) { // currentInput not a duplicate; assign to array[i]
            array[i] = currentInput;
            i++;
        }

Regarding exiting on providing -1, You should probably remove this line array[i] = 0 in order to not assign 0 to array[i]:

if (array[i] != -1) {
    // ...
} else {
    System.out.println("Exit Confirmed");
    System.out.println("Press Any Key To Continue...");
    new Scanner(System.in).nextLine();
    System.out.print('\u000C');
    break;
}

Answer 2

Here are some errors I found in your code:

• You go to newline in System.out.plintln("Enter the " + array.length + "...."); in the middle of the string, you should do something like that:

System.out.println("Enter the " + array.length + " numbers now." + "\nOr enter -1 to exit")

• if the input is -1 you don't exit straight away but you do array[i]=0 (remember that array[i] now is array[-1])
• then you don't break the loop after -1 is inputted
• case shouldn't be enclosed in brackets and should always finish with break:

case 1:
  //DO THINGS
  //....
  //...
  break;
case 2:
  //DO OTHER THINGS
  //....
  //...
  break;

Here are some suggestions on how to improve it:

• I don't remember very well Java, but I don't think you have to create a new Scanner every time
• if I was you I would check if the input is -1 as the first thing (there are several ways to do that)
• not using the brackets for the for is a bit confusing
• you already break when a duplicate is found, so you don't need to check it again with if(!dups)

I hope this solves your problem.