How to Implement linear search in Java? A Complete Guide

Before we move onto the Java implementation of Linear Search, let's first discuss the pseudocode of the algorithm. Aishwarya Rai does that in the video below.

In the above video at the timestamp 1:27, the instructor intends to place the return -1 out of the scope of for loop. The modified pseudocode is as follows.

int key;
int array[];

for (int i=0; i<array.length(); i++) {
       if(array[i] == key) {
                 return i; }
}

return -1;

Video Transcript

So now let us try to see how we can write a simple pseudocode for the linear search algorithm. So here I can see a variable declared called key which is the key which I want to find. And here is my array. This array denotes the collection of objects in which I have to find whether a key exists or not. So what I'll do carefully look at this statement here, you will see that I'm comparing the array of I and key. So this basically denotes that I'm comparing the is element of the array with the key and checking if they are equal or not. If they are equal, I return I which is the index of the element which matches with the key. And since I have to repeat this process for each and every element of the array so I have written a for loop here. In this case I'm beginning my for loop from index I equals to zero and moving it till I reach the end of the array. And in each step I'm incrementing my i. Now, when this whole iteration would end and if I'm still unable to find whether the key exists in this array or not, and suppose I reach the end of the array, then towards the end I can just say return minus one. So since minus one cannot be an index in this array, returning minus one would indicate that my key has not been found in the given array. So this was a very basic pseudocode of implementing linear search.

Video Recap

• The linear search algorithm is used to find whether a key exists in an array or not.

• To write the pseudocode for the linear search algorithm, a key variable is declared to find a key in the array.

• A for loop is used to iterate through each element of the array, comparing it with the key.

• If a match is found, the index of the element is returned. If no match is found, -1 is returned.

• The -1 indicates that the key does not exist in the given array.

Now that you are comfortable with the pseudocode of the algorithm, it's time to see the code in action. Please download the Java file for the code given below.