list1.java

java容器方面的各种应用

//: c09:List1.java
// From 'Thinking in Java, 2nd ed.' by Bruce Eckel
// www.BruceEckel.com. See copyright notice in CopyRight.txt.
// Things you can do with Lists.
import java.util.*;
import com.bruceeckel.util.*;

public class List1 {
  public static List fill(List a) {
    Collections2.countries.reset();
    Collections2.fill(a, 
      Collections2.countries, 10);
    return a;
  }
  static boolean b;
  static Object o;
  static int i;
  static Iterator it;
  static ListIterator lit;
  public static void basicTest(List a) {
    a.add(1, "x"); // Add at location 1
    a.add("x"); // Add at end
    // Add a collection:
    a.addAll(fill(new ArrayList()));
    // Add a collection starting at location 3:
    a.addAll(3, fill(new ArrayList())); 
    b = a.contains("1"); // Is it in there?
    // Is the entire collection in there?
    b = a.containsAll(fill(new ArrayList()));
    // Lists allow random access, which is cheap
    // for ArrayList, expensive for LinkedList:
    o = a.get(1); // Get object at location 1
    i = a.indexOf("1"); // Tell index of object
    b = a.isEmpty(); // Any elements inside?
    it = a.iterator(); // Ordinary Iterator
    lit = a.listIterator(); // ListIterator
    lit = a.listIterator(3); // Start at loc 3
    i = a.lastIndexOf("1"); // Last match 
    a.remove(1); // Remove location 1
    a.remove("3"); // Remove this object
    a.set(1, "y"); // Set location 1 to "y"
    // Keep everything that's in the argument
    // (the intersection of the two sets):
    a.retainAll(fill(new ArrayList()));
    // Remove everything that's in the argument:
    a.removeAll(fill(new ArrayList()));
    i = a.size(); // How big is it?
    a.clear(); // Remove all elements
  }
  public static void iterMotion(List a) {
    ListIterator it = a.listIterator();
    b = it.hasNext();
    b = it.hasPrevious();
    o = it.next();
    i = it.nextIndex();
    o = it.previous();
    i = it.previousIndex();
  }
  public static void iterManipulation(List a) {
    ListIterator it = a.listIterator();
    it.add("47");
    // Must move to an element after add():
    it.next();
    // Remove the element that was just produced:
    it.remove(); 
    // Must move to an element after remove():
    it.next();
    // Change the element that was just produced:
    it.set("47");
  }
  public static void testVisual(List a) {
    System.out.println(a);
    List b = new ArrayList();
    fill(b);
    System.out.print("b = ");
    System.out.println(b);
    a.addAll(b);
    a.addAll(fill(new ArrayList()));
    System.out.println(a);
    // Insert, remove, and replace elements
    // using a ListIterator:
    ListIterator x = a.listIterator(a.size()/2);
    x.add("one"); 
    System.out.println(a);
    System.out.println(x.next());
    x.remove();
    System.out.println(x.next());
    x.set("47");
    System.out.println(a);
    // Traverse the list backwards:
    x = a.listIterator(a.size());
    while(x.hasPrevious())
      System.out.print(x.previous() + " ");
    System.out.println();
    System.out.println("testVisual finished");
  }
  // There are some things that only
  // LinkedLists can do:
  public static void testLinkedList() {
    LinkedList ll = new LinkedList();
    fill(ll);
    System.out.println(ll);
    // Treat it like a stack, pushing:
    ll.addFirst("one");
    ll.addFirst("two");
    System.out.println(ll);
    // Like "peeking" at the top of a stack:
    System.out.println(ll.getFirst());
    // Like popping a stack:
    System.out.println(ll.removeFirst());
    System.out.println(ll.removeFirst());
    // Treat it like a queue, pulling elements
    // off the tail end:
    System.out.println(ll.removeLast());
    // With the above operations, it's a dequeue!
    System.out.println(ll);
  }
  public static void main(String[] args) {
    // Make and fill a new list each time:
    basicTest(fill(new LinkedList()));
    basicTest(fill(new ArrayList()));
    iterMotion(fill(new LinkedList()));
    iterMotion(fill(new ArrayList()));
    iterManipulation(fill(new LinkedList()));
    iterManipulation(fill(new ArrayList()));
    testVisual(fill(new LinkedList()));
    testLinkedList();
  }
} ///:~