Problem

Create a method that accepts an array of integers and a key integer value x to determine whether or not the key value exists in the given array. The method should return true if the key value was found in the array, otherwise the method should return false.

Array Algorithms

Solution

Let's start with creating the skeleton of our method with the proper return type and accepted parameter values.

public static boolean elementExists(int[] array, int x) {

}

We'll want to keep a boolean variable to keep track of whether or not you have found the key value x. At the beginning of your method, initialize this boolean variable to false since you have not yet found the key value. This will also be the value to return at the end of the method.

boolean exists = false;

return exists;

Use a for loop to go through each element in the array to check if it is the value we're looking for.

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

}

For each element in the array, use an if statement to compare each element with the given key value. In order to compare each element with the key value, use the '==' operator. If the current element is equal to the key value, that means you have found the element in the array so you can set your boolean variable to true.

if(array[i] == x) {
    exists = true;
}

Putting everything together, here's what the entire method should look like:

public static boolean elementExists(int[] array, int x) {
    int i; // loop iterator
    boolean exists = false;

    for(i = 0; i < array.length; i++) {
        if(array[i] == x) {
            exists = true;
        }
    }

    return exists;
}

Code

Solution Code

/*
This program creates an array of ten random numbers between 0 and 15 
and asks the user to input a value to check whether or not it is 
in the random array
*/

import javax.swing.JOptionPane;

public class LinearSearchForX {
    public static void main(String args[]) {
        int i, x;
	int[] numbers = new int[10];
	boolean xFound = false;

	// Create an array of random numbers
	for(i = 0; i < numbers.length; i++) {
	    numbers[i] = (int)(Math.random() * 15); // generates a random number from 0-15
	    System.out.println("numbers["+i+"] = "+numbers[i]);
	}

	// Ask user to input a value to search for
	x = Integer.ParseInt(JOptionPane.showInputDialog(null, "Enter a value between (0-15) to search for:"));

	// Call your method to check if the element exists
	xFound = elementExists(numbers, x);

	// Display the results of your search.
	if(xFound) {
	    System.out.println(x+" was found in the array");
	} else {
	    System.out.println(x+" was not found in the array");
	}
    }

    public static boolean elementExists(int[] array, int x) {
        int i; // loop iterator
        boolean exists = false;
        for(i = 0; i < array.length; i++) {
            if(array[i] == x) {
                exists = true;
            }
        }

        return exists;
    }

}