Binary Search Example in Java

Introduction

Binary Search is a classic Java console program that demonstrates the concept with complete source code and sample output. Classic data structures such as stack, queue and linked list implemented in Java.

This tutorial walks through the program line by line, explains how the logic works, and highlights best practices you can apply in your own code.

Definition

A straightforward implementation of binary search is recursive. The initial call uses the indices of the entire array to be searched. The procedure then calculates an index midway between the two indices, determines which of the two subarrays to search, and then does a recursive call to search that subarray. Each of the calls is tail recursive, so a compiler need not make a new stack frame for each call. The variables imin and imax are the lowest and highest inclusive indices that are searched.

Binary Search Example Program

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
public class BinarySearchMain {

    public static void main(String arg[]) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BinarySearch binarySearch = new BinarySearch(10);
        binarySearch.readData();
        System.out.println("Enter the Element to search");
        int find = Integer.parseInt(br.readLine());
        int index = binarySearch.search(find);

        if (index != -1) {
            System.out.println("Element found Position : " + (index+1));
        } else {
            System.out.println("Element not found");
        }
    }
}

class BinarySearch {

    private int data[];
    private int size;

    public BinarySearch(int size) {
        this.data = new int[size];
        this.size = size;
    }

    public void readData() throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Please Enter Values");
        for (int i = 0; i < size; i++) {
            System.out.println("Enter Value #"+(i+1)+" : ");
            data[i] = Integer.parseInt(br.readLine());
        }
    }

    public int search(int find) {
        int start = 0;
        int end = data.length - 1;
        int mid;
        while (start <= end) {
            mid = (start + end) / 2;
            if (data[mid] == find) {
                return mid;
            } else if (data[mid] < find) {
                start = mid + 1;
            } else if (data[mid] > find) {
                end = mid - 1;
            }
        }
        return -1;
    }
}

Sample Output

Please Enter Values
Enter Value #1 : 
34
Enter Value #2 : 
11
Enter Value #3 : 
22
Enter Value #4 : 
45
Enter Value #5 : 
78
Enter the Element to search
45
Element found Position : 4

When to use

Use this binary search example when learning or revising core Java syntax.

How it works

1. Execution begins in the main method — the JVM calls this method when you run the class.

2. import java.io.BufferedReader; imports a class used later in the program.

3. import java.io.IOException; imports a class used later in the program.

4. import java.io.InputStreamReader; imports a class used later in the program.

5. BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); updates a variable used in the calculation or output.

6. BinarySearch binarySearch = new BinarySearch(10); updates a variable used in the calculation or output.

7. A println / print call writes text to the console — part of the sample output below.

8. The if statement runs the nested code only when the condition is true.

Best Practices

• Use meaningful variable and class names that describe their purpose.
• Compile and run the program locally — modify values to see how output changes.
• Read compiler errors carefully; they usually point to the exact line to fix.

Common Mistakes

• Copying code without understanding each line — practice by changing one statement at a time.
• Mismatching the public class name and the .java filename.
• Forgetting semicolons at the end of statements.