集合オブジェクト-「ブロック・データ」アクション--実は同じオブジェクト参照

例:
Set  set1 = new HashSet();
set1.add( object1 );
set1.add( ... );
set1.add( objectn );
Set set2 = new HashSet(  set1 );
または
Set  set3 = new HashSet( set1 );
set3.addAll( set1 );
set 2とset 3に格納されているのはset 1要素の「参照」です.
コードは次のとおりです.

/**
 *   addAll( Collections )
 *  。
 * @author gqltt
 *
 */
public class SetAddAllTest {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		testSetWithPerson();
	}
	
	private static <T> void print( String desc, Set<T> set ){
		System.out.println( desc );
		for( T s : set ){
			System.out.print( s + "  ");
		}
		System.out.println( "
" );
	}
	
	/**
	 *  
	 */
	private static void testSetWithPerson(){
		Set<Person> set1 = new HashSet<Person>();
		set1.add( new Person("b", 25) );
		set1.add( new Person("a", 20) );
		set1.add( new Person("c", 26) );
		
		Set<Person> set2 = new TreeSet<Person>();
		set2.addAll( set1 );
		
		//
		print( "set1", set1 );
		print( "set2", set2 );
		
		changeName( getPersonByName( set1, "a" ), "abc" );
		print( "set1 after modify element Person {name a->abc }:", set1 );
		print( "set2 after set1 modify element:", set2 );
	}
	
	private static Person getPersonByName( Set<Person> set, String name ){
		for( Person p : set ){
			if( p.name.equals( name ) ){
				return p;
			}
		}
		return null;
	}
	
	private static void changeName( Person p, String newName ){
		p.setName( newName );
	}
	static class Person implements Comparable<Person>{
		private String name;
		
		private int age;

		
		public Person(String name, int age) {
			super();
			this.name = name;
			this.age = age;
		}

		public String getName() {
			return name;
		}

		public void setName(String name) {
			this.name = name;
		}

		public int getAge() {
			return age;
		}

		public void setAge(int age) {
			this.age = age;
		}

		@Override
		public String toString() {
			return "(" + name + ", " + age + ")";
		}

		@Override
		public int compareTo(Person person) {
			return age - person.age;
		}

		@Override
		public boolean equals(Object obj) {
			if( obj == null ){
				return false;
			}
			if( ! ( getClass() == obj.getClass() ) ){
				return false;
			}
			Person p = (Person) obj;
			return name != null && name.equals( p.name ) && age == p.age;
		}

		@Override
		public int hashCode() {
			int result = 47;
			result += name.hashCode();
			result += new Integer( age ).hashCode();
			return result;
		}
		
	}

}

テスト結果出力:
set1 (b, 25) (c, 26) (a, 20) set2 (a, 20) (b, 25) (c, 26) set1 after modify element Person {name a->abc }: (b, 25) (c, 26) (abc, 20) set2 after set1 modify element: (abc, 20) (b, 25) (c, 26)