collections2.java

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//: com:bruceeckel:util:Collections2.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// To fill any type of container 
// using a generator object.
package com.bruceeckel.util;
import java.util.*;

public class Collections2 {
  // Fill an array using a generator:
  public static void 
  fill(Collection c, Generator gen, int count) {
    for(int i = 0; i < count; i++)
      c.add(gen.next());
  }
  public static void 
  fill(Map m, MapGenerator gen, int count) {
    for(int i = 0; i < count; i++) {
      Pair p = gen.next();
      m.put(p.key, p.value);
    }
  }
  public static class RandStringPairGenerator
  implements MapGenerator {
    private Arrays2.RandStringGenerator gen;
    public RandStringPairGenerator(int len) {
      gen = new Arrays2.RandStringGenerator(len);
    }
    public Pair next() {
      return new Pair(gen.next(), gen.next());
    }
  }
  // Default object so you don't have 
  // to create your own:
  public static RandStringPairGenerator rsp =
    new RandStringPairGenerator(10);
  public static class StringPairGenerator
  implements MapGenerator {
    private int index = -1;
    private String[][] d;
    public StringPairGenerator(String[][] data) {
      d = data;
    }
    public Pair next() {
      // Force the index to wrap:
      index = (index + 1) % d.length;
      return new Pair(d[index][0], d[index][1]);
    }
    public StringPairGenerator reset() { 
      index = -1; 
      return this;
    }
  }
  // Use a predefined dataset:
  public static StringPairGenerator geography =
    new StringPairGenerator(
      CountryCapitals.pairs);
  // Produce a sequence from a 2D array:
  public static class StringGenerator
  implements Generator {
    private String[][] d;
    private int position;
    private int index = -1;
    public 
    StringGenerator(String[][] data, int pos) {
      d = data;
      position = pos;
    }
    public Object next() {
      // Force the index to wrap:
      index = (index + 1) % d.length;
      return d[index][position];
    }
    public StringGenerator reset() { 
      index = -1;
      return this;
    }
  }
  // Use a predefined dataset:
  public static StringGenerator countries =
    new StringGenerator(CountryCapitals.pairs,0);
  public static StringGenerator capitals =
    new StringGenerator(CountryCapitals.pairs,1);
} ///:~