Language: Java

public class Main {
  private static class FastScanner {
    private BufferedReader reader = null;
    private StringTokenizer tokenizer = null;

    public FastScanner(InputStream in) {
      reader = new BufferedReader(new InputStreamReader(in));
      tokenizer = null;
    }

    public String next() {
      if (tokenizer == null || !tokenizer.hasMoreTokens()) {
        try {
          tokenizer = new StringTokenizer(reader.readLine());
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
      }
      return tokenizer.nextToken();
    }

    public String nextLine() {
      if (tokenizer == null || !tokenizer.hasMoreTokens()) {
        try {
          return reader.readLine();
        } catch (IOException e) {
          throw new RuntimeException(e);
        }
      }

      return tokenizer.nextToken("\n");
    }

    public long nextLong() {
      return Long.parseLong(next());
    }

    public int nextInt() {
      return Integer.parseInt(next());
    }

    public double nextDouble() {
      return Double.parseDouble(next());
    }

    public int[] nextIntArray(int n) {
      int[] a = new int[n];
      for (int i = 0; i < n; i++)
        a[i] = nextInt();
      return a;
    }

    public long[] nextLongArray(int n) {
      long[] a = new long[n];
      for (int i = 0; i < n; i++)
        a[i] = nextLong();
      return a;
    }
  }

  public static void main(String[] args) {
    FastScanner sc = new FastScanner(System.in);
    String s = sc.next();
    String t = sc.next();
    int tLen = t.length();
    int result = tLen;
    for (int i = 0; i + tLen <= s.length(); i++) {
      int diff = 0;
      for (int j = 0; j < tLen; j++) {
        if (t.charAt(j) != s.charAt(i + j)) diff++;
      }
      result = Math.min(result, diff);
    }
    System.out.println(result);
  }
}

Compiler output:
Main.java:3: error: cannot find symbol
    private BufferedReader reader = null;
            ^
  symbol:   class BufferedReader
  location: class FastScanner
Main.java:4: error: cannot find symbol
    private StringTokenizer tokenizer = null;
            ^
  symbol:   class StringTokenizer
  location: class FastScanner
Main.java:6: error: cannot find symbol
    public FastScanner(InputStream in) {
                       ^
  symbol:   class InputStream
  location: class FastScanner
Main.java:7: error: cannot find symbol
      reader = new BufferedReader(new InputStreamReader(in));
                   ^
  symbol:   class BufferedReader
  location: class FastScanner
Main.java:7: error: cannot find symbol
      reader = new BufferedReader(new InputStreamReader(in));
                                      ^
  symbol:   class InputStreamReader
  location: class FastScanner
Main.java:14: error: cannot find symbol
          tokenizer = new StringTokenizer(reader.readLine());
                          ^
  symbol:   class StringTokenizer
  location: class FastScanner
Main.java:15: error: cannot find symbol
        } catch (IOException e) {
                 ^
  symbol:   class IOException
  location: class FastScanner
Main.java:26: error: cannot find symbol
        } catch (IOException e) {
                 ^
  symbol:   class IOException
  location: class FastScanner
8 errors