Qfyilyi

I have an assignment to create an int array that is serched in another method for a user input int value then displays the index of that element in the array. I have that part working just fine and I personaly chose to make the elements in the array random values from 1 - 10.I also need to have the program display a message ("Element not found in array") in the event that the given number isn't in the array. I cannot seem to get this part to work correctly and am hoping I can get some advice here.

import java.util.Scanner;



public class NeedleInHaystack {



public static void main(String args) {

    Scanner scan = new Scanner(System.in);



    System.out.println("Please provide an Integer for the needle: ");

    int needle = scan.nextInt();

    int haystack = new int[10];



    System.out.println("The array being used is: ");



    for (int i = 0; i < 10; i++) {

        int j = (int) (Math.random() * 9 + 1);

        haystack[i] = j;

        System.out.print(haystack[i] + " ");

    }



    returnIndex(haystack, needle);



}



public static int returnIndex(int haystack, int needle) {

    int index = needle;

    System.out.println("nThe needle is found at index: ");



    for (int i = 0; i < haystack.length; i++) {

        if (haystack[i] == index) {

            System.out.println(i);

        }

    }



    return index;

 }



}

The program is an int needle in a hastack array. What is the best way to make the program end "gracefully" in the event that the input value is not present in the random array?

The assignment was worded as follows:
"Create a Java program with a method that searches an integer array for a specified integer value (see help with starting the method header below). If the array contains the specified integer, the method should return its index in the array. If not, the method should throw an Exception stating "Element not found in array" and end gracefully. Test the method in main with an array that you make and with user input for the "needle"."

You could add some sort of boolean flag in the method that you set to true if it is found. If not, the flag will remain false. After iterating through the array, you could check whether the flag is false and if so, then you could print some error message.

public static int returnIndex(int haystack, int needle) {



    boolean found = false;



    int index = needle;

    System.out.println("nThe needle is found at index: ");



    for (int i = 0; i < haystack.length; i++) {

        if (haystack[i] == index) {

            System.out.println(i);

            found = true;

        }

    }



    if (found) return index;



    else  {



        System.out.println("Not found.");

        return null;



    }





 }



}

Problem is in for-loop your are checking the needle in array but not return it, and also since you have assigned int index = needle; at the beginning, even though if needle is not in array it will return needle

So in that case assign index=0 in beginning and iterate the array, if found return the index else return the needle

public static int returnIndex(int haystack, int needle) {

int index;

System.out.println("nThe needle is found at index: ");



for (index = 0; index < haystack.length; index++) {

    if (haystack[index] == needle) {

      System.out.println("value found at index"+index);

        return index;

    }

   }

   System.out.println("The value not found in array");



   return needle;;

}

Since you are supposed to return the index and not the needle value you should just return inside the for-loop once the object is found. Very Similar to what Deadpool did.

But as you state the method is supposed to throw a exception when the needle isn‘t found you should get rid of the second return statement and just throw a exception.

public static int returnIndex(int haystack, int needle) {

    System.out.println("nThe needle is found at index: ");



    for (int i = 0; i < haystack.length; i++) {

        if (haystack[i] == needle) {

            System.out.println(i);

            return i;

        }

    }



    throw new NoSuchElementException(„Element not found in array“);

 }