How to change the amount and the content of its data

Question

i'm trying to make data search and sort with switch case. i have to input the amount of data and its members. for example:

amount of data: //for example: 2
input the data(s):

data num-1 : //user input
data num-2 : //user input

selection

case 1: //data search

case 2: //bubblesort

case 3: //selectionsort

case 4: //edit

i stuck at case 4. i've tried my code but the amount of data and the current doesn't changes at all and if i want to change the amount of data with bigger number than before, the index out of the bound. here's the code.

    public static void main(String[] args) {

    Scanner s=new Scanner(System.in);
    int n;
    System.out.println("-------------------data search and sort-------------------");
    System.out.println("");
    System.out.println("");
    System.out.println("Hai ");
    System.out.print("How many datas do you want? : ");
    n=s.nextInt();
    int bil[]=new int[n]; //bil is array
    System.out.println("input the data:");
    for(int i=1;i<=n;i++){
        System.out.print(" data -" +i+ " = ");
        bil[i-1]=s.nextInt();
    }
    System.out.println("");
    System.out.println("");
    while(true){
    
    System.out.println("Displaying data(s) : ");
    for(int i: bil){
        System.out.print(i+" ");
    }
    System.out.println("");
    System.out.println("Menu:");
    System.out.println("\t1. Search data");
    System.out.println("\t2. Bubblesort ascending");
    System.out.println("\t3. SelectionSort descending");
    System.out.println("\t4. Edit");
    System.out.println("\t5. Exit");
    System.out.print("What's your choice? : ");
    int pilih=s.nextInt();
    switch(pilih){
        case 1:
            System.out.println("Enter the number you are looking for = ");
            int srch = s.nextInt();
            boolean found = false;
            for(int index=0; index<bil.length; index++) {
            if(bil[index] == srch){
            found = true;
                }
            }
            if(found == true) {
            System.out.println("Found '"+srch + "' in data collection!");
            } else {
            System.out.println(srch + "there is no data you're looking for here");
            }
            System.out.println("");
            
            System.out.println("Displaying data : ");
            for(int i: bil){
            System.out.print(i+" ");
            }
            System.out.println("");
            System.out.print("Continue? (y/n)");
            String conti = s.next();
           
            boolean nue;
            switch(con){
            case "y":
            nue = false;
            break;
            case "n": 
                return;
            }
            break;
        case 2: 
             
            System.out.println("BubbleSorting is done!");
            System.out.println("");
            System.out.println("Displaying data(s) :");
            int i, j, te;
            for (i = 0; i < n; i++)
                for (i = 0; i < ( n - 1 ); i++) {
                    for (j = 0; j < n - i - 1; j++) {
                        if (bil[j] > bil[j+1]){
                            te = bil[j];
                            bil[j] = bil[j+1];
                            bil[j+1] = te;
                        }
                    }
            }
            for (i = 0; i < n; i++) {
                System.out.print(bil[i]);
            }
           
            System.out.print("Continue? (y/n)");
            conti = s.next();
            switch(conti){
            case "y":
            nue = false;
            break;
            case "n": 
                return;
            }
            break;
        case 3:
            for (i = 0; i < n; i++){
                for (j = i + 1; j < n; j++){
                    if (bil[i] < bil[j]){
                        te = bil[i];
                        bil[i] = bil[j];
                        bil[j] = te;
                    }
                }
            }
            System.out.print("SelectionSort is done");
            System.out.println("");
            System.out.println("Displaying data(s):");
            for (i = 0; i < n - 1; i++){
                System.out.print(bil[i] + " ");
            }
            System.out.print(bil[n - 1]);
            System.out.println("");
            System.out.print("Continue? (y/n)");
            conti = s.next();
            switch(conti){
            case "y":
            nue = false;
            break;
            case "n": 
                return;
            }
            break;
        case 4:
            System.out.print("WARNING!!! the data will be change!");
            System.out.print("continue? (y/t)");
            String change = s.next();
           
            boolean edit;
            switch(change){
            case "y":
            System.out.print("How many datas do you want? = ");
            n=s.nextInt();
            System.out.println("Input the data");
            for(i=1;i<=n;i++){
            System.out.print(" data -" +i+ " = ");
            bil[n]=s.nextInt();
            edit = false;
            }
            break;
            case "n": 
                return;
            }
            
            break;
        }    
    }

ps: i do not forget to import java.util.Scanner

When you ask "How many datas do you want?" in case 4, are you asking the number of new data points to add in addition to the originally entered data? Or are you expecting to discard the originally entered data and get a completely new set of data points? — Udith Gunaratna, Aug 06 '20 at 08:06
i am expecting to discard the originally entered data and get a completely new set of data points — Juan Charistheas Hawu, Aug 06 '20 at 15:05

score 0 · Accepted Answer · answered Aug 06 '20 at 10:05

Hey the issue here is that you are already declaring the array as int bil = new int[n]; So in your 4th case when you take another "n" as input which is larger than the previous "n" , it throws the ArrayIndexOutOfBoundsException.You need to increase the size of array before storing more values in it.Add the following code in your 4th case after taking the new "n" as input:

    bil = Arrays.copyOf(bil,n);

You should refer to this answer for more info:Resize an Array while keeping current elements in Java?

score 0 · Answer 2 · answered Aug 07 '20 at 11:41

Since you need to discard the originally entered data and get a completely new set of data points, first you need to create a new array with the new number of data points. Then you need to assign the user inputs to that array.

case 4:
    System.out.print("WARNING!!! the data will be change!");
    System.out.print("continue? (y/t)");
    String change = s.next();

    boolean edit;
    switch (change) {
        case "y":
            System.out.print("How many datas do you want? = ");
            n = s.nextInt();

            // Create a new array and assign it to the same variable bil
            bil = new int[n];

            System.out.println("Input the data");
            for (i = 1; i <= n; i++) {
                System.out.print(" data -" + i + " = ");

                // Add data point to the (i-1)th position of the array
                bil[i - 1] = s.nextInt();
                edit = false;
            }
            break;
        case "n":
            return;
    }

How to change the amount and the content of its data

2 Answers2