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CrypLetterMapping.java
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CrypLetterMapping.java
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package crypSwing;
import java.util.*;
/**
* This class maps one ciphertext letter to every possible plaintext letter to which it can translate.
* @author Bitman
* @version 2.0 01/20/21
*/
public class CrypLetterMapping {
private String possiblePlaintextLetters;
/**
* This constructor builds the map based on whether the user chose like-exclusion.
* @param initialValue The set of all letters to which we initially guess a ciphertext character might map
*/
public CrypLetterMapping(String initialValue) {
possiblePlaintextLetters = initialValue;
}
/**
* Eliminate a set of characters from the list of possible plaintext letters.
* Note that this method includes some validation, namely making sure that the list isn't narrowed down to zero letters.
* @param lettersToEliminate The characters to eliminate, validation permitting
*/
public void eliminateLetters(String lettersToEliminate) {
int index;
for (index=0; index < lettersToEliminate.length(); index++) {
if (possiblePlaintextLetters.length() <= 1) return;
possiblePlaintextLetters = possiblePlaintextLetters.replaceFirst(lettersToEliminate.substring(index, index+1), "");
}
}
/**
* Get a new list of characters, intersect it with the existing possibilities, and if
* there's anything left, set the possible plaintext letters to that intersection.
* Note that this method assumes that the list of characters is in alphabetical order.
* @param newList The new list of possible plaintext characters
*/
void narrowDownLetters(List<Character> newList) {
String temp = "";
for (Character c : newList)
if (possiblePlaintextLetters.contains(c.toString()))
temp += c;
if (temp != "") possiblePlaintextLetters = temp;
}
/**
* Determine whether the current mapping allows a given plaintext character.
* @param plaintext The plaintext character
* @return true if the mapping allows the character, false otherwise
*/
public boolean allows(String plaintext) {
return possiblePlaintextLetters.contains(plaintext);
}
/**
* Determine the size of the mapping - that is, how many possible plaintext letters there are.
* @return The number of possible plaintext letters.
*/
public int size() {
return possiblePlaintextLetters.length();
}
/**
* Return what possible plaintext letters there are.
* @return The number of possible plaintext letters.
*/
public String possiblePlaintext() {
return possiblePlaintextLetters;
}
}