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從code學習java tiger之自動裝箱拆箱

Posted on 2006-06-22 18:34 BlueO2 閱讀(403) 評論(0) 編輯收藏所屬分類: JAVA foundation

public ? class ?AutoBoxing? {

????

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

???? public ?AutoBoxing()? {

????}

???? public ? void ?boxingDemo() {

???????? // auto?boxing

????????Integer?i? = ? 0 ;

???????? float ?f? = ? 1.66f ;

????????Float?F? = ?f;

???????? // auto?unboxing

????????Integer?I? = ? new ?Integer( 1 );

???????? int ?i2? = ?I;

???????? // null?value?test,?it?will?case?NullPointerException

????????Integer?I2? = ? null ;

???????? int ?i3? = ?I2;

????}

???? public ? void ?testOperator() {

????????Integer?i? = ? 1 ;

???????? while ( true ) {

????????????i ++ ;

????????????System.out.println( " Counter: " + i);

???????????? if (i > 5 )? break ;

????????}

????}

???? public ? void ?testCompare() {

???????? // it's?equal?because?-127~127?are?immutable?objects

????????Integer?i? = ? 1 ;

????????Integer?i2? = ? 1 ;

???????? if (i? == ?i2)?System.out.println( " 1:Equal " );

???????? else ?System.out.println( " 1:Not?Equal " );

???????? // it's?not?equal?because?j?and?j2?are?different?objects

????????Integer?j? = ? 200 ;

????????Integer?j2? = 200 ;

???????? if (j? == ?j2)?System.out.println( " 200:Equal " );

???????? else ?System.out.println( " 200:Not?Equal " );

????}

???? public ? void ?testControl() {

????????Boolean?flag? = ? true ;

????????Integer?i? = ? 20 ;

????????Integer?j? = ? 30 ;

???????? if (flag) {

????????????System.out.println( " Boolean?affects " );

????????}

???????? if (i < j)

????????????System.out.println( " Integer?affects " );

????}

???? public ? void ?testMethod( double ?arg) {

????????System.out.println( " public?void?testMethod(double?arg)?is?invoked " );

????}

???? public ? void ?testMethod(Integer?arg) {

????????System.out.println( " public?void?testMethod2(Integer?arg)?is?invoked " );

????}

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

????????AutoBoxing?auto? = ? new ?AutoBoxing();

????????auto.testCompare();

????????auto.testOperator();

????????auto.testControl();

???????? int ?i? = ? 1 ;

???????? // ?public?void?testMethod(Integer?arg)?wouldn't?be?invoked

???????? // because??public?void?testMethod(double?arg)?will?be?invoked?in?JDK1.4

???????? // Java?tiger?consider?the?backward?capability

????????auto.testMethod(i);

????????auto.boxingDemo();

????}

????

}

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