maps.java

Thinking in JAVA第四版源代码

//: containers/Maps.java
// Things you can do with Maps.
import java.util.concurrent.*;
import java.util.*;
import net.mindview.util.*;
import static net.mindview.util.Print.*;

public class Maps {
  public static void printKeys(Map<Integer,String> map) {
    printnb("Size = " + map.size() + ", ");
    printnb("Keys: ");
    print(map.keySet()); // Produce a Set of the keys
  }
  public static void test(Map<Integer,String> map) {
    print(map.getClass().getSimpleName());
    map.putAll(new CountingMapData(25));
    // Map has 'Set' behavior for keys:
    map.putAll(new CountingMapData(25));
    printKeys(map);
    // Producing a Collection of the values:
    printnb("Values: ");
    print(map.values());
    print(map);
    print("map.containsKey(11): " + map.containsKey(11));
    print("map.get(11): " + map.get(11));
    print("map.containsValue(\"F0\"): "
      + map.containsValue("F0"));
    Integer key = map.keySet().iterator().next();
    print("First key in map: " + key);
    map.remove(key);
    printKeys(map);
    map.clear();
    print("map.isEmpty(): " + map.isEmpty());
    map.putAll(new CountingMapData(25));
    // Operations on the Set change the Map:
    map.keySet().removeAll(map.keySet());
    print("map.isEmpty(): " + map.isEmpty());
  }
  public static void main(String[] args) {
    test(new HashMap<Integer,String>());
    test(new TreeMap<Integer,String>());
    test(new LinkedHashMap<Integer,String>());
    test(new IdentityHashMap<Integer,String>());
    test(new ConcurrentHashMap<Integer,String>());
    test(new WeakHashMap<Integer,String>());
  }
} /* Output:
HashMap
Size = 25, Keys: [15, 8, 23, 16, 7, 22, 9, 21, 6, 1, 14, 24, 4, 19, 11, 18, 3, 12, 17, 2, 13, 20, 10, 5, 0]
Values: [P0, I0, X0, Q0, H0, W0, J0, V0, G0, B0, O0, Y0, E0, T0, L0, S0, D0, M0, R0, C0, N0, U0, K0, F0, A0]
{15=P0, 8=I0, 23=X0, 16=Q0, 7=H0, 22=W0, 9=J0, 21=V0, 6=G0, 1=B0, 14=O0, 24=Y0, 4=E0, 19=T0, 11=L0, 18=S0, 3=D0, 12=M0, 17=R0, 2=C0, 13=N0, 20=U0, 10=K0, 5=F0, 0=A0}
map.containsKey(11): true
map.get(11): L0
map.containsValue("F0"): true
First key in map: 15
Size = 24, Keys: [8, 23, 16, 7, 22, 9, 21, 6, 1, 14, 24, 4, 19, 11, 18, 3, 12, 17, 2, 13, 20, 10, 5, 0]
map.isEmpty(): true
map.isEmpty(): true
...
*///:~