A key is a value that you are looking for in an array.

The simplest type of search is the sequential search. In the sequential search, each element of the array is compared to the key, in the order it appears in the array, until the desired element is found.

If you are looking for an element that is near the front of the array, the sequential search will find it quickly. The more data that must be searched, the longer it will take to find the data that matches the key.

public static int search(int [ ] numbers, int key)

{

       for (int index = 0; index < numbers.length; index++)

      {

           if ( numbers[index] = = key )

                 return index;  //We found it!!!

      }

     // If we get to the end of the loop, a value has not yet

     // been returned.  We did not find the key in this array.

     return -1;

}

If the key value is found, the index (subscript) of the location is returned. This tells us that the return value x, will be the first integer found such that
numbers [ x ] = key.

There may be additional key locations in this array beyond this location.

Now, suppose you are searching for
the number of times
a specific key value is included in an array:

//Find the number of times the name "Jones" appears in an array of name

public static void main(String[] args)

{

    String key = "Jones";

    String[ ] list = new String [100];   // instantiate the array

    for ( int i=0; i<100; i++)     // fill the array

         list [ i ]=Console.readLine("Enter name:  ");

    int count = search (list, key);    // invoke the method

    System.out.println("Count = " + count);

}

public static int search(String [ ] list, String key) //method to find "Jones"

{

     int i, count = 0;

     for( i = 0; i< list.length; i++)

     {

          if (list [ i ].equals( key ))

             count = count+1;

     }

     return (count);

}