Java CookBook--Using a Bag--by Tim O'Brien 整理by博主

  Bag可以储存一个对象很多副本，并跟踪这些副本

  实例如下:

Bag bag=new HashBag();
bag.add("TEST1",100);
bag.add("TEST2",500);
int test1Count=bag.getCount("TEST1");
int test2Count = bag.getCount( "TEST2" );
System.out.println( "Counts: TEST1: " + test1Count + ", TEST2: " + test2Count );
bag.remove("TEST1",1);
bag.remove( "TEST2", 10 );
test1Count = bag.getCount( "TEST1" );
test2Count = bag.getCount( "TEST2" );
System.out.println( "Counts: TEST1: " + test1Count + ", TEST2: " + test2Count );Bag bag=n