map1.java

几个简单的java学习代码

import java.util.*;

public class Map1 {
  public final static String[][] testData1 = {
    { "Happy", "Cheerful disposition" },
    { "Sleepy", "Prefers dark, quiet places" },
    { "Grumpy", "Needs to work on attitude" },
    { "Doc", "Fantasizes about advanced degree"},
    { "Dopey", "'A' for effort" },
    { "Sneezy", "Struggles with allergies" },
    { "Bashful", "Needs self-esteem workshop"},
  };
  public final static String[][] testData2 = {
    { "Belligerent", "Disruptive influence" },
    { "Lazy", "Motivational problems" },
    { "Comatose", "Excellent behavior" }
  };
  public static Map fill(Map m, Object[][] o) {
    for(int i = 0; i < o.length; i++)
      m.put(o[i][0], o[i][1]);
    return m;
  }
  // Producing a Set of the keys:
  public static void printKeys(Map m) {
    System.out.print("Size = " + m.size() +", ");
    System.out.print("Keys: ");
    Collection1.print(m.keySet());
  }
  // Producing a Collection of the values:
  public static void printValues(Map m) {
    System.out.print("Values: ");
    Collection1.print(m.values());
  }
  // Iterating through Map.Entry objects (pairs):
  public static void print(Map m) {
    Collection entries = m.entrySet();
    Iterator it = entries.iterator();
    while(it.hasNext()) {
      Map.Entry e = (Map.Entry)it.next();
      System.out.println("Key = " + e.getKey() +
        ", Value = " + e.getValue());
    }
  }
  public static void test(Map m) {
    fill(m, testData1);
    // Map has 'Set' behavior for keys:
    fill(m, testData1);
    printKeys(m);
    printValues(m);
    print(m);
    String key = testData1[4][0];
    String value = testData1[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));

    printKeys(m);
    m.remove(testData1[0][0]);
    printKeys(m);
    m.clear();
    System.out.println("m.isEmpty(): "
      + m.isEmpty());
    fill(m, testData1);
    // Operations on the Set change the Map:
    m.keySet().removeAll(m.keySet());
    System.out.println("m.isEmpty(): "
      + m.isEmpty());
  }
  public static void main(String args[]) {
    System.out.println("Testing HashMap");
    test(new HashMap());
  }
} ///:~

运行结果：

Size = 7, Keys: Dopey Doc Happy Sneezy Grumpy Sleepy Bashful 

Values: 'A' for effort Fantasizes about advanced degree Cheerful disposition Struggles with allergies Needs to work on attitude Prefers dark, quiet places Needs self-esteem workshop 

Key = Dopey, Value = 'A' for effort

Key = Doc, Value = Fantasizes about advanced degree

Key = Happy, Value = Cheerful disposition

Key = Sneezy, Value = Struggles with allergies

Key = Grumpy, Value = Needs to work on attitude

Key = Sleepy, Value = Prefers dark, quiet places

Key = Bashful, Value = Needs self-esteem workshop

m.containsKey("Dopey"): true

m.get("Dopey"): 'A' for effort

m.containsValue("'A' for effort"): true

Size = 7, Keys: Dopey Doc Happy Sneezy Grumpy Sleepy Bashful 

Size = 6, Keys: Dopey Doc Sneezy Grumpy Sleepy Bashful 

m.isEmpty(): true

m.isEmpty(): true