KMP String Matching Algorithm

　　This is a program based on Knuth-Morris-Pratt String Matching Algorithm (a.k.a KMP algorithm), which can be tapped to solve the problem POJ 3461.

import java.io.*;
import java.util.*;

class Input {
    private Scanner in;
    private StringTokenizer tok;
    
    public Input() {
        in = new Scanner(new BufferedInputStream(System.in));
    }
    public String nextString() {
        while  (tok==null||!tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.nextLine());
        } 
        return tok.nextToken();
    }
    public int nextInt() {
        while  (tok==null||!tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.nextLine());
        } 
        return Integer.parseInt(tok.nextToken());
    }
    public double nextDouble() {
        while  (tok==null||!tok.hasMoreTokens()) {
            tok = new StringTokenizer(in.nextLine());
        } 
        return Double.parseDouble(tok.nextToken());
    }
    public void close() {
        in.close();
    }
}

public class Main {
    
    public static int[] preproc(String pattern)  {
        int[] dp = new int[pattern.length()];
        Arrays.fill(dp,-1);
        for (int i=1;i<pattern.length();i++) {
            for (int j=i-1;j>=0;j=dp[j]) {
                if (pattern.charAt(dp[j]+1)==pattern.charAt(i)) {
                    dp[i] = dp[j]+1;
                    break;
                }
            }
        }
        return dp;
    }
    public static int match(String pattern,String test) {
        int[] next = preproc(pattern);
        int cnt = 0;
        for (int i=0,j=0;i<test.length();) {
            if (test.charAt(i)==pattern.charAt(j)) {
                ++i;
                if (++j==pattern.length()) {
                    cnt++;
                    j = next[j-1]+1;
                }
            } else if (j>0) {
                j = next[j-1]+1;
            } else {
                i++;
            }
        }
        return cnt;
    }
    public static void main(String[] args) {
        Input in = new Input();
        int time = in.nextInt();
        for (int t=0;t<time;t++) {
            System.out.println(match(in.nextString(),in.nextString()));
        }
        in.close();
    }
}