Tech review ch02

CCSPiJ/src/chapter2/Gene.java

@@ -28,21 +28,21 @@ public enum Nucleotide {
 
 	public static class Codon implements Comparable<Codon> {
 		public final Nucleotide first, second, third;
+		private final Comparator<Codon> comparator = Comparator.comparing((Codon c) -> c.first)
+				.thenComparing((Codon c) -> c.second)
+				.thenComparing((Codon c) -> c.third);
 
 		public Codon(String codonStr) {
-			first = Enum.valueOf(Nucleotide.class, codonStr.substring(0, 1));
-			second = Enum.valueOf(Nucleotide.class, codonStr.substring(1, 2));
-			third = Enum.valueOf(Nucleotide.class, codonStr.substring(2, 3));
+			first = Nucleotide.valueOf(codonStr.substring(0, 1));
+			second = Nucleotide.valueOf(codonStr.substring(1, 2));
+			third = Nucleotide.valueOf(codonStr.substring(2, 3));
 		}
 
 		@Override
 		public int compareTo(Codon other) {
 			// first is compared first, then second, etc.
 			// IOW first takes precedence over second and second over third
-			return Comparator.comparing((Codon c) -> c.first)
-					.thenComparing((Codon c) -> c.second)
-					.thenComparing((Codon c) -> c.third)
-					.compare(this, other);
+			return comparator.compare(this, other);
 		}
 	}
 

CCSPiJ/src/chapter2/GenericSearch.java

@@ -21,6 +21,7 @@
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.Map;
 import java.util.PriorityQueue;
 import java.util.Queue;
 import java.util.Set;
@@ -31,7 +32,7 @@
 
 public class GenericSearch {
 
-	public static <T extends Comparable<T>> boolean linearContains(List<T> list, T key) {
+	public static <T extends Comparable<? super T>> boolean linearContains(List<T> list, T key) {
 		for (T item : list) {
 			if (item.compareTo(key) == 0) {
 				return true; // found a match
@@ -41,7 +42,7 @@ public static <T extends Comparable<T>> boolean linearContains(List<T> list, T k
 	}
 
 	// assumes *list* is already sorted
-	public static <T extends Comparable<T>> boolean binaryContains(List<T> list, T key) {
+	public static <T extends Comparable<? super T>> boolean binaryContains(List<T> list, T key) {
 		int low = 0;
 		int high = list.size() - 1;
 		while (low <= high) { // while there is still a search space
@@ -161,7 +162,7 @@ public static <T> Node<T> astar(T initial, Predicate<T> goalTest,
 		PriorityQueue<Node<T>> frontier = new PriorityQueue<>();
 		frontier.offer(new Node<>(initial, null, 0.0, heuristic.applyAsDouble(initial)));
 		// explored is where we've been
-		HashMap<T, Double> explored = new HashMap<>();
+		Map<T, Double> explored = new HashMap<>();
 		explored.put(initial, 0.0);
 		// keep going while there is more to explore
 		while (!frontier.isEmpty()) {
@@ -186,9 +187,9 @@ public static <T> Node<T> astar(T initial, Predicate<T> goalTest,
 	}
 
 	public static void main(String[] args) {
-		System.out.println(GenericSearch.linearContains(List.of(1, 5, 15, 15, 15, 15, 20), 5)); // true
-		System.out.println(GenericSearch.binaryContains(List.of("a", "d", "e", "f", "z"), "f")); // true
-		System.out.println(GenericSearch.binaryContains(List.of("john", "mark", "ronald", "sarah"), "sheila")); // false
+		System.out.println(linearContains(List.of(1, 5, 15, 15, 15, 15, 20), 5)); // true
+		System.out.println(binaryContains(List.of("a", "d", "e", "f", "z"), "f")); // true
+		System.out.println(binaryContains(List.of("john", "mark", "ronald", "sarah"), "sheila")); // false
 	}
 
 }

CCSPiJ/src/chapter2/MCState.java

@@ -24,11 +24,11 @@
 
 public class MCState {
 	private static final int MAX_NUM = 3;
-	final private int wm; // west bank missionaries
-	final private int wc; // west bank cannibals
-	final private int em; // east bank missionaries
-	final private int ec; // east bank cannibals
-	final private boolean boat; // is boat on west bank?
+	private final int wm; // west bank missionaries
+	private final int wc; // west bank cannibals
+	private final int em; // east bank missionaries
+	private final int ec; // east bank cannibals
+	private final boolean boat; // is boat on west bank?
 
 	public MCState(int missionaries, int cannibals, boolean boat) {
 		wm = missionaries;
@@ -109,13 +109,11 @@ public static void displaySolution(List<MCState> path) {
 		System.out.println(oldState);
 		for (MCState currentState : path.subList(1, path.size())) {
 			if (currentState.boat) {
-				System.out.printf("%d missionaries and %d cannibals moved from the east bank to the west bank." +
-						System.lineSeparator(),
+				System.out.printf("%d missionaries and %d cannibals moved from the east bank to the west bank.%n",
 						oldState.em - currentState.em,
 						oldState.ec - currentState.ec);
 			} else {
-				System.out.printf("%d missionaries and %d cannibals moved from the west bank to the east bank." +
-						System.lineSeparator(),
+				System.out.printf("%d missionaries and %d cannibals moved from the west bank to the east bank.%n",
 						oldState.wm - currentState.wm,
 						oldState.wc - currentState.wc);
 			}

CCSPiJ/src/chapter2/Maze.java

@@ -25,23 +25,21 @@
 public class Maze {
 
 	public enum Cell {
-		EMPTY, BLOCKED, START, GOAL, PATH;
+		EMPTY(" "),
+		BLOCKED("X"),
+		START("S"),
+		GOAL("G"),
+		PATH("*");
+
+		private final String code;
+
+		private Cell(String c) {
+			code = c;
+		}
 
 		@Override
 		public String toString() {
-			switch (this) {
-			case EMPTY:
-				return (" ");
-			case BLOCKED:
-				return ("X");
-			case START:
-				return ("S");
-			case GOAL:
-				return ("G");
-			case PATH:
-				return ("*");
-			}
-			return null; // should never get here
+			return code;
 		}
 	}
 
@@ -129,7 +127,7 @@ public String toString() {
 		StringBuilder sb = new StringBuilder();
 		for (Cell[] row : grid) {
 			for (Cell cell : row) {
-				sb.append(cell.toString());
+				sb.append(cell);
 			}
 			sb.append(System.lineSeparator());
 		}