Java connect four game

Question:

Connect four game in java.

Code:

import java.util.Scanner;
 
public class ConnectFour {
 
  public static String[][] createPattern() {
 
    String[][] f = new String[7][15];
 
    for (int i =0;i<f.length;i++) {
 
       for (int j =0;j<f[i].length;j++) {
        if (j% 2 == 0){
           f[i][j] ="|";
        } else {
           f[i][j] = " ";
        }
 
        if (i==6) f[i][j]= "-";
      }
 
    }
    return f;
  }
 
  public static void printPattern(String[][] f) {
    for (int i =0;i<f.length;i++) {
      for (int j=0;j<f[i].length;j++) {
        System.out.print(f[i][j]);
      }
      System.out.println();
    }
  }
 
  public static void dropRedPattern(String[][] f) {
    System.out.print("Drop a red disk at column (0–6): ");
    Scanner scan = new Scanner (System.in);
    int c = 2*scan.nextInt()+1;
    for (int i =5;i>=0;i--) {
      if (f[i][c] == " ") {
        f[i][c] = "R";
        break;
      }
    }
  }
 
  public static void dropBlackPattern(String[][] f) {
    System.out.print("Drop a black disk at column (0–6): ");
    Scanner scan = new Scanner (System.in);
    int c = 2*scan.nextInt()+1;
    for (int i =5;i>=0;i--) {
      if (f[i][c] == " ") {
        f[i][c] = "B";
        break;
      }
    }
  }
 
 
  public static String checkWinner(String[][] f) {
    for (int i =0;i<6;i++) {
      for (int j=0;j<7;j+=2) {
        if ((f[i][j+1] != " ")
        && (f[i][j+3] != " ")
        && (f[i][j+5] != " ")
        && (f[i][j+7] != " ")
        && ((f[i][j+1] == f[i][j+3])
        && (f[i][j+3] == f[i][j+5])
        && (f[i][j+5] == f[i][j+7])))
 
          return f[i][j+1]; 
      }
    }
 
    for (int i=1;i<15;i+=2) {
      for (int j =0;j<3;j++) {
            if((f[j][i] != " ")
            && (f[j+1][i] != " ")
            && (f[j+2][i] != " ")
            && (f[j+3][i] != " ")
            && ((f[j][i] == f[j+1][i])
            && (f[j+1][i] == f[j+2][i])
            && (f[j+2][i] == f[j+3][i])))
              return f[j][i]; 
      } 
    }
 
    for (int i=0;i<3;i++) {
 
      for (int j=1;j<9;j+=2) {
            if((f[i][j] != " ")
            && (f[i+1][j+2] != " ")
            && (f[i+2][j+4] != " ")
            && (f[i+3][j+6] != " ")
            && ((f[i][j] == f[i+1][j+2])
            && (f[i+1][j+2] == f[i+2][j+4])
            && (f[i+2][j+4] == f[i+3][j+6])))
              return f[i][j]; 
      } 
    }
 
    for (int i=0;i<3;i++) {
      for (int j=7;j<15;j+=2) {
            if((f[i][j] != " ")
            && (f[i+1][j-2] != " ")
            && (f[i+2][j-4] != " ")
            && (f[i+3][j-6] != " ")
            && ((f[i][j] == f[i+1][j-2])
            && (f[i+1][j-2] == f[i+2][j-4])
            && (f[i+2][j-4] == f[i+3][j-6])))
              return f[i][j]; 
      } 
    }
 
    return null;
  }
 
  public static void main (String[] args) {
    String[][] f = createPattern();
    boolean loop = true;
    int count = 0;
    printPattern(f);
    while(loop) {
      if (count % 2 == 0) dropRedPattern(f);
      else dropBlackPattern(f);
      count++;
      printPattern(f);
      if (checkWinner(f) != null) {
        if (checkWinner(f) == "R"){
           System.out.println("Red won.");
        } else if (checkWinner(f)== "B") {
          System.out.println("Black won.");
        }
        loop = false;
      }
    }
  }
}

Output:

$ java ConnectFour
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
---------------
Drop a red disk at column (0–6): 1
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| |R| | | | | |
---------------
Drop a black disk at column (0–6): 0
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
|B|R| | | | | |
---------------
Drop a red disk at column (0–6): 1
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| |R| | | | | |
|B|R| | | | | |
---------------
Drop a black disk at column (0–6): 2
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| |R| | | | | |
|B|R|B| | | | |
---------------
Drop a red disk at column (0–6): 1
| | | | | | | |
| | | | | | | |
| | | | | | | |
| |R| | | | | |
| |R| | | | | |
|B|R|B| | | | |
---------------
Drop a black disk at column (0–6): 6
| | | | | | | |
| | | | | | | |
| | | | | | | |
| |R| | | | | |
| |R| | | | | |
|B|R|B| | | |B|
---------------
Drop a red disk at column (0–6): 1
| | | | | | | |
| | | | | | | |
| |R| | | | | |
| |R| | | | | |
| |R| | | | | |
|B|R|B| | | |B|
---------------
Red won.