Java Program to Implement the String Search Algorithm for Short Text Sizes

This is a java program to search string using simple algorithm BoyerMoore.

Here is the source code of the Java Program to Implement the String Search Algorithm for Short Text Sizes. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

package com.maixuanviet.setandstring;
 
import java.util.Scanner;
 
class BoyerMoore
{
    private final int BASE;
    private int[]     occurrence;
    private String    pattern;
 
    public BoyerMoore(String pattern)
    {
        this.BASE = 256;
        this.pattern = pattern;
        occurrence = new int[BASE];
        for (int c = 0; c < BASE; c++)
            occurrence = -1;
        for (int j = 0; j < pattern.length(); j++)
            occurrence[pattern.charAt(j)] = j;
    }
 
    public int search(String text)
    {
        int n = text.length();
        int m = pattern.length();
        int skip;
        for (int i = 0; i <= n - m; i += skip)
        {
            skip = 0;
            for (int j = m - 1; j >= 0; j--)
            {
                if (pattern.charAt(j) != text.charAt(i + j))
                {
                    skip = Math.max(1, j - occurrence[text.charAt(i + j)]);
                    break;
                }
            }
            if (skip == 0)
                return i;
        }
        return n;
    }
}
 
public class StringSearch
{
    public static void main(String[] args)
    {
        Scanner sc = new Scanner(System.in);
        System.out.print("Enter the main string: ");
        String text = sc.nextLine();
        System.out.print("Enter the string to be searched: ");
        String pattern = sc.nextLine();
        BoyerMoore bm = new BoyerMoore(pattern);
        int first_occur_position = bm.search(text);
        System.out.println("The text '" + pattern
                + "' is first found after the " + first_occur_position
                + " position.");
        sc.close();
    }
}

Output:

$ javac StringSearch.java
$ java StringSearch
 
Enter the main string: I will soon be working in Redmond USA with Mircosoft.
Enter the string to be searched: soon
The text 'soon' is first found after the 7 position.