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從codes學java tiger之范型

Posted on 2006-06-20 18:18 BlueO2 閱讀(398) 評論(0) 編輯收藏所屬分類: JAVA foundation

public ? class ?Generic? {

????

???? /** ?Creates?a?new?instance?of?Generic? */

???? public ?Generic()? {

????}

????

???? public ? void ?collectionGeneric() {

???????? // generic?list

????????List < String > ?onlyStrings? = ? new ?LinkedList < String > ();

????????onlyStrings.add( " Legal?addition " );

???????? // generic?map

????????Map < Integer,?Integer > ?squares? = ? new ?HashMap < Integer,?Integer > ();

???????? for ?( int ?i = 0 ;?i < 100 ;?i ++ )? {

????????????squares.put(i,?i * i);

????????}

???????? for ?( int ?i = 0 ;?i < 10 ;?i ++ )? {

???????????? int ?n? = ?i * 3 ;

????????????System.out.println( " The?square?of? " ? + ?n? + ? " ?is? " ? + ?squares.get(n));

????????}

???????? // generic?iterator

????????List < String > ?listOfStrings? = ? new ?LinkedList < String > ();

????????listOfStrings.add( " Happy " );

????????listOfStrings.add( " Birthday " );

???????? for ?(Iterator < String > ?i? = ?listOfStrings.iterator();?i.hasNext(?);?)? {

????????????String?s? = ?i.next(?);

????????????System.out.println(s);

????????}

????}

???? // parameter?generic

???? public ? void ?paramGeneric(List < String > ?list) {

???????? for (Iterator < String > ?i? = ?list.iterator();i.hasNext();) {

????????????String?s? = ?i.next();

????????????System.out.println(s);

????????}

????}

???? // return?generic

???? public ?List < String > ?returnGeneric() {

????????List < String > ?list? = ? new ?LinkedList < String > ();

????????list.add( " string1 " );

???????? return ?list;

????}

???? // conversion

???? public ? void ?conversionGeneric() {

????????LinkedList < Float > ?floatList? = ? new ?LinkedList < Float > ();

????????List < Float > ?moreFloats? = ?floatList;

???????? // illegal?conversion?LinkedList<Number>?numberList?=?floatList;

???????? // the?way?to?resolve?for?backward?capbility

????????List < Integer > ?ints? = ? new ?LinkedList < Integer > ();

????????List?oldList? = ?ints;

????????List < Number > ?numList? = ?oldList;

????}

???? // generic?wildcard?:?this?old?plain?way?will?generate?unchecked?warning

???? public ? void ?wildcardGeneric(List?list) {

???????? for ?(Iterator?i? = ?list.iterator();?i.hasNext();?)? {

????????????System.out.println(i.next().toString());

????????}

????}

???? // generic?wildcard

???? public ? void ?wildcardGeneric2(List <?> ?list) {

???????? // you?can't?solve?the?problem?by?List<Object>

???????? for ?(Iterator <?> ?i? = ?list.iterator(?);?i.hasNext();?)? {

????????????System.out.println(i.next().toString(?));

????????}

????}

????

}

/**

?*?public?class?Box<T?extends?Number>

?*? @author ?david.duan

? */

public ? class ?Box < T > ? {

????

???? // you?can't?have?a?static?variable?such?as?protected?static?List<T>?list

???? protected ?List < T > ?contents;

????

???? public ?Box(?)? {

????????contents? = ? new ?ArrayList < T > (?);

????}

???? public ? int ?getSize(?)? {

???????? return ?contents.size(?);

????}

???? public ? boolean ?isEmpty(?)? {

???????? return ?(contents.size(?)? == ? 0 );

????}

???? public ? void ?add(T?o)? {

????????contents.add(o);

????}

???? public ?T?grab(?)? {

???????? if ?( ! isEmpty(?))? {

???????????? return ?contents.remove( 0 );

????????} ? else

???????????? return ? null ;

????}

???? public ? static ? void ?main(String[]?args) {

????????Box < String > ?box? = ? new ?Box < String > ();

???????? //

????}

}

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