map1.java

Java编程思想 第九课 全源码

//: c09:Map1.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// Things you can do with Maps.
import java.util.*;
import com.bruceeckel.util.*;

public class Map1 {
  static Collections2.StringPairGenerator geo = 
    Collections2.geography;
  static Collections2.RandStringPairGenerator 
    rsp = Collections2.rsp;
  // Producing a Set of the keys:
  public static void printKeys(Map m) {
    System.out.print("Size = " + m.size() +", ");
    System.out.print("Keys: ");
    System.out.println(m.keySet());
  }
  // Producing a Collection of the values:
  public static void printValues(Map m) {
    System.out.print("Values: ");
    System.out.println(m.values());
  }
  public static void test(Map m) {
    Collections2.fill(m, geo, 5);
    // Map has 'Set' behavior for keys:
    Collections2.fill(m, geo.reset(), 5);
    printKeys(m);
    printValues(m);
    System.out.println(m);
    String key = CountryCapitals.pairs[4][0];
    String value = CountryCapitals.pairs[4][1];
    System.out.println("m.containsKey(\"" + key +
      "\"): " + m.containsKey(key));
    System.out.println("m.get(\"" + key + "\"): "
      + m.get(key));
    System.out.println("m.containsValue(\"" 
      + value + "\"): " + 
      m.containsValue(value)); 
    Map m2 = new TreeMap();
    Collections2.fill(m2, rsp, 5);
    m.putAll(m2);
    printKeys(m);
    key = m.keySet().iterator().next().toString();
    System.out.println("First key in map: "+key);
    m.remove(key);
    printKeys(m);
    m.clear();
    System.out.println("m.isEmpty(): " 
      + m.isEmpty());
    Collections2.fill(m, geo.reset(), 5);
    // Operations on the Set change the Map:
    m.keySet().removeAll(m.keySet());
    System.out.println(m+ "\t" +"m.isEmpty(): "
      + m.isEmpty());
  }
  public static void main(String[] args) {
    System.out.println("Testing HashMap");
    test(new HashMap());
    System.out.println("Testing TreeMap");
    test(new TreeMap());
  }
} ///:~