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Semester 1/Programming 1/Java/examples/projects/chapter07/automaton-v1/Automaton.java

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+import java.util.Arrays;
+
+/**
+ * Model a 1D elementary cellular automaton.
+ * 
+ * @author David J. Barnes and Michael Kölling
+ * @version  2016.02.29 - version 1
+ */
+public class Automaton
+{
+    // The number of cells.
+    private final int numberOfCells;
+    // The state of the cells.
+    private int[] state;
+    
+    /**
+     * Create a 1D automaton consisting of the given number of cells.
+     * @param numberOfCells The number of cells in the automaton.
+     */
+    public Automaton(int numberOfCells)
+    {
+        this.numberOfCells = numberOfCells;
+        state = new int[numberOfCells];
+        // Seed the automaton with a single 'on' cell in the middle.
+        state[numberOfCells / 2] = 1;
+    }
+    
+    /**
+     * Print the current state of the automaton.
+     */
+    public void print()
+    {
+        for(int cellValue : state) {
+            if(cellValue == 1) {
+                System.out.print("*");
+            }
+            else {
+                System.out.print(" ");
+            }
+        }
+        System.out.println();
+    }   
+    
+    /**
+     * Update the automaton to its next state.
+     */
+    public void update()
+    {
+        // Build the new state in a separate array.
+        int[] nextState = new int[state.length];
+        // Naively update the state of each cell
+        // based on the state of its two neighbors.
+        for(int i = 0; i < state.length; i++) {
+            int left, center, right;
+            if(i == 0) {
+                left = 0;
+            }
+            else {
+                left = state[i - 1];
+            }
+            center = state[i];
+            if(i + 1 < state.length) {
+                right = state[i + 1];
+            }
+            else {
+                right = 0;
+            }
+            nextState[i] = (left + center + right) % 2;
+        }
+        state = nextState;
+    }
+    
+    /**
+     * Reset the automaton.
+     */
+    public void reset()
+    {
+        Arrays.fill(state, 0);
+        // Seed the automaton with a single 'on' cell.
+        state[numberOfCells / 2] = 1;
+            
+    }
+}