Initial data commit

Task/Bifid-cipher/Java/bifid-cipher.java

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+import java.awt.Point;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public final class BifidCipher {
+
+	public static void main(String[] aArgs) {
+		final String message1 = "ATTACKATDAWN";
+		final String message2 = "FLEEATONCE";
+		final String message3 = "The invasion will start on the first of January".toUpperCase().replace(" ", "");
+		
+		Bifid bifid1 = new Bifid(5, "ABCDEFGHIKLMNOPQRSTUVWXYZ");
+		Bifid bifid2 = new Bifid(5, "BGWKZQPNDSIOAXEFCLUMTHYVR");
+		
+		runTest(bifid1, message1);
+		runTest(bifid2, message2);
+		runTest(bifid2, message1);
+		runTest(bifid1, message2);
+		
+		Bifid bifid3 = new Bifid(6, "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789");
+		runTest(bifid3, message3);
+	}	
+	
+	private static void runTest(Bifid aBifid, String aMessage) {
+		System.out.println("Using Polybius square:");
+		aBifid.display();
+		System.out.println("Message:   " + aMessage);
+		String encrypted = aBifid.encrypt(aMessage);
+		System.out.println("Encrypted: " + encrypted);
+		String decrypted = aBifid.decrypt(encrypted);
+		System.out.println("Decrypted: " + decrypted);
+		System.out.println();
+	}	
+	
+}
+	
+final class Bifid {
+	
+	public Bifid(int aN, String aText) {
+		if ( aText.length() != aN * aN ) {
+			throw new IllegalArgumentException("Incorrect length of text");
+		}
+		
+		grid = new char[aN][aN];			
+		int row = 0;
+		int col = 0;		
+		for ( char ch : aText.toCharArray() ) {
+		    grid[row][col] = ch;
+		    coordinates.put(ch, new Point(row, col) );
+		    col += 1;
+		    if ( col == aN ) {
+		    	col = 0;
+		    	row += 1;
+		     }
+		 }
+		
+		 if ( aN == 5 ) {
+		     coordinates.put('J', coordinates.get('I'));
+		 }
+	}	
+	
+	public String encrypt(String aText) {		
+		List<Integer> rowOne = new ArrayList<Integer>();
+		List<Integer> rowTwo = new ArrayList<Integer>();
+		for ( char ch : aText.toCharArray() ) {
+			Point coordinate = coordinates.get(ch);
+			rowOne.add(coordinate.x);
+			rowTwo.add(coordinate.y);
+		 }
+		
+		 rowOne.addAll(rowTwo);
+		 StringBuilder result = new StringBuilder();
+		 for ( int i = 0; i < rowOne.size() - 1; i += 2 ) {
+			 result.append(grid[rowOne.get(i)][rowOne.get(i + 1)]);
+		 }
+		 return result.toString();
+	}
+	
+	public String decrypt(String aText) {
+		List<Integer> row = new ArrayList<Integer>();
+		for ( char ch : aText.toCharArray() ) {
+			Point coordinate = coordinates.get(ch);
+		    row.add(coordinate.x);
+		    row.add(coordinate.y);
+		}
+		
+		final int middle = row.size() / 2;
+		List<Integer> rowOne = row.subList(0, middle);
+		List<Integer> rowTwo = row.subList(middle, row.size());
+		StringBuilder result = new StringBuilder();
+		for ( int i = 0; i < middle; i++ ) {
+			result.append(grid[rowOne.get(i)][rowTwo.get(i)]);
+		}
+		return result.toString();
+	}
+
+    public void display() {
+		Arrays.stream(grid).forEach( row -> System.out.println(Arrays.toString(row)) );
+	}
+	
+	private char[][] grid;
+	private Map<Character, Point> coordinates = new HashMap<Character, Point>();
+	
+}