SubstitutionCipher

import java.lang.Math;
import java.util.ArrayList;

public class SubstitutionCipher {

  private String symbolBank = "!@#$%^&*()_+-={}[]|./?<>:\"";
  private String letterBank = "abcdefghijklmnopqrstuvwxyz";

  private String[][] wordBank = {
    {"a", "i"},
    {"an", "at", "as", "go", "hi", "or", "if", "is", "in", "it", "me", "my", "am", "be", "to", "of", "so", "us", "we"},
    {"and", "the", "for", "but", "are", "not", "you", "all", "any", "can", "her", "was", "one", "our", "out", "day", "get", "has", "him", "his", "how", "man", "new", "now", "old", "men", "see", "two", "way", "who", "boy", "did", "its", "let", "put", "say", "she", "too", "use", "dad", "mom", "try", "why"}
  };

  public String encode(String message) {
    message = message.toLowerCase();
    String b;
    if ((int)(Math.random()*2) == 0) {
      b = symbolBank;
    } else {
      b = letterBank;
    }
    char[] bank = b.toCharArray();
    String output = "";
    for (int i = 0; i < message.length(); i++) {
      output += "_";
    }
    boolean[] tracker = new boolean[message.length()];
    for (int i = 0; i < message.length(); i++) {
      System.out.print(i + ": ");
      if (!tracker[i]) {
        System.out.print("Replacing... ");
        if ((int)message.charAt(i)>=65 && (int)message.charAt(i)<=122) {
          char a = nextReplacement(message.charAt(i), bank);
          System.out.println(message.charAt(i) + " with " + a);
          for (int v = i; v < message.length(); v++) {
            if (message.charAt(v) == message.charAt(i)) {
              output = transcribe(output, v, a);
              tracker[v] = true;
            }
          }
        } else {
          System.out.println("Failed. Non alphanumeric.");
          //output = transcribe(output, i, message.charAt(i));
          output = transcribe(output, i, ' ');
          tracker[i] = true;
        }
      } else {
        System.out.println("Failed. Already replaced.");
      }
    }
    return output;
  }

  public char nextReplacement(char a, char[] b) {
    int index;
    while (true) {
      index = (int)(Math.random()*b.length);
      if (b[index] != '`' && b[index] != a) {
        break;
      }
    }
    char choice = b[index];
    b[index] = '`';
    return choice;
  }

  public String transcribe(String s, int i, char b) {
    return  s.substring(0, i) + b + s.substring(i+1);
  }

  public String decode(String message) {
    String[][] messageBank = tabulateMessage(message);
    for (int i = 0; i < messageBank.length; i++) {
      for (int v = 0; v < messageBank[0].length; v++) {
        System.out.print(messageBank[i][v] + " ");
      }
      System.out.println("");
    }
    for (int len = 0; len < wordBank.length; len++) {

    }
    return "";
  }

  public String[][] tabulateMessage(String message) {
    boolean flag = false;
    int wordnum = 0;
    for (int i = 0; i < message.length(); i++) {
      if ((int)message.charAt(i)>=65 && (int)message.charAt(i)<=122) {
        flag = true;
        if (i == message.length()-1) {
          wordnum++;
        }
      } else if (flag) {
        flag = false;
        wordnum++;
      }
    }
    System.out.println(wordnum + " words");
    flag = false;
    int[] counter = new int[wordnum];
    int wordlen = 0;
    int wordmax = 0;
    for (int i = 0; i < message.length(); i++) {
      if ((int)message.charAt(i)>=65 && (int)message.charAt(i)<=122) {
        flag = true;
        wordlen++;
        if (i == message.length()-1) {
          if (wordlen > wordmax) {
            wordmax = wordlen;
          }
          counter[wordlen-1]++;
        }
      } else if (flag) {
        flag = false;
        if (wordlen > wordmax) {
          wordmax = wordlen;
        }
        counter[wordlen-1]++;
        wordlen=0;
      }
    }
    int lenmax = 0;
    for (int i = 0; i < counter.length; i++) {
      if (counter[i] > lenmax) {
        lenmax = counter[i];
      }
    }

    String[][] messageWords = new String[wordmax][lenmax];
    int[] tracker = new int[wordmax];
    flag = false;
    wordlen = 0;
    for (int i = 0; i < message.length(); i++) {
      if ((int)message.charAt(i)>=65 && (int)message.charAt(i)<=122) {
        flag = true;
        wordlen++;
        if (i == message.length()-1) {
          messageWords[wordlen-1][tracker[wordlen-1]] = message.substring(i-wordlen+1);
          tracker[wordlen-1]++;
        }
      } else if (flag) {
        messageWords[wordlen-1][tracker[wordlen-1]] = message.substring(i-wordlen, i);
        tracker[wordlen-1]++;
        flag = false;
        wordlen=0;
      }
    }
    return messageWords;
  }

  public void error(String text) {
    throw new IllegalArgumentException(text);
  }
}