[B! java][Null] kana321ã®ãƒ–ãƒƒã‚¯ãƒžãƒ¼ã‚¯

kana321 id:kana321

javaã¨Nullã«é–¢ã™ã‚‹kana321ã®ãƒ–ãƒƒã‚¯ãƒžãƒ¼ã‚¯ (6)

${{author_name}}$

{{{comment_expanded}}}

{{label}}

{{#is_bookmark}}ãƒªã‚¹ãƒˆ{{/is_bookmark}}{{^is_bookmark}}ãƒªãƒ³ã‚¯{{/is_bookmark}}

${{author_name}}$
{{author_name}}{{created}}
{{ #comment }}{{ comment }}{{ /comment }}
- {{ label }}

${{author_name}}$

{{{comment_expanded}}}

{{label}}

{{#is_bookmark}}ãƒªã‚¹ãƒˆ{{/is_bookmark}}{{^is_bookmark}}ãƒªãƒ³ã‚¯{{/is_bookmark}}

è„±ãƒ“ã‚®ãƒŠãƒ¼ï¼Androidã®nullãªè©± - ã‚¯ãƒƒã‚¯ãƒ‘ãƒƒãƒ‰é–‹ç™ºè€…ãƒ–ãƒã‚°
æ–°è¦åºƒå‘Šé–‹ç™ºéƒ¨ã®æ¾æœ¬ã§ã™ã€‚ ã‚¯ãƒƒã‚¯ãƒ‘ãƒƒãƒ‰iOS/Androidã‚¢ãƒ—ãƒªã®åºƒå‘Šã®é–‹ç™ºã«æºã‚ã£ã¦ã„ã¾ã™ã€‚ Androidã‚¢ãƒ—ãƒªé–‹ç™ºã®éš›ã€çš†ã•ã‚“ã¯nullã‚’ã©ã®ã‚ˆã†ã«æ‰±ã£ã¦ã„ã¾ã™ã‹ï¼Ÿã¾ãŸã€nullãƒã‚§ãƒƒã‚¯ã‚’è¡Œã†ã®ã§ã‚ã‚Œã°ã€ã©ã®ã‚ˆã†ãªåŸºæº–ã§è¡Œã£ã¦ã„ã¾ã™ã‹ï¼Ÿç§è‡ªèº«ã¾ã ã¾ã Androidé–‹ç™ºæ´ãŒæµ…ã„ãŸã‚ã€ç‰¹ã«ä½•ã‹åŸºæº–ãŒã‚ã‚‹è¨³ã§ã‚‚ãªãè‡³ã‚‹æ‰€ã§if (foo != null)ã¨ã„ã£ãŸnullãƒã‚§ãƒƒã‚¯ã‚’è¡ŒãŠã†ã¨ã—ã¦ã„ã¾ã—ãŸã€‚ ã“ã‚Œã«å¯¾ã—ã€å…ˆæ—¥ã®ç¤¾å†…ã‚³ãƒ¼ãƒ‰ãƒ¬ãƒ“ãƒ¥ãƒ¼ã§ã¨ã¦ã‚‚ãŸã‚ã«ãªã‚‹ã‚¢ãƒ‰ãƒã‚¤ã‚¹ã‚’ã‚‚ã‚‰ã„ã¾ã—ãŸã€‚ç§ã®ã‚ˆã†ãªAndroidåˆå¿ƒè€…ã«ã¨ã£ã¦nullã«å¯¾ã™ã‚‹è€ƒãˆæ–¹ã®åŸºç¤Žã‚’ä½œã£ã¦ãã‚Œã‚‹ãƒ¬ãƒ“ãƒ¥ãƒ¼ã ã£ãŸã®ã§ã€æœ¬ç¨¿ã§å…±æœ‰ã—ãŸã„ã¨æ€ã„ã¾ã™ã€‚ ã¾ãŸã€Androidã‚„Javaé–‹ç™ºã«æ…£ã‚ŒãŸæ–¹ã«ã¨ã£ã¦ã¯ã€Œä»Šæ›´ãã‚“ãªè©±ã‹ã€ã¨ã„ã£ãŸå†…å®¹ã‹ã¨æ€ã„ã¾ã™ãŒã€ã‚¯ãƒƒã‚¯ãƒ‘ãƒƒãƒ‰ã§ã®ãƒ¬ãƒ“ãƒ¥ãƒ¼ã®ä¸€ä¾‹ã¨ã—ã¦ã”è¦§ã„ãŸã ã‘ã‚Œã°å¹¸ã„ã§ã™ã€‚ ã‚„ã‚ŠãŒã¡ãªnul
kana321 2015/02/21
Androidé–‹ç™º

*1

()

android

java

null

ã‚ã¨ã§èªã‚€

programming

é–‹ç™º

Androidã‚¢ãƒ—ãƒª
ãƒªãƒ³ã‚¯
Nullãªã®ã¯ã„ã‘ãªã„ã¨æ€ã„ã¾ã™ï¼
1. Null was used as an exception to point out issues. 2. Null used three sentences to summarize the key details. 3. Null's summary highlighted the object, option, exception handling, and Kotlin programming language.
kana321 2014/11/23
*programming

**

kotlin

programming

ãƒ›ãƒƒãƒˆã‚¨ãƒ³ãƒˆãƒª

scala

java

Null

ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°

slideshare
ãƒªãƒ³ã‚¯
nullä½¿ã£ãŸã‚‰è² ã‘ç¦å²¡ç‰ˆ
ãƒ’ã‚šãƒ¥ã‚¢JavaãŸã‚™ã¨æ€ã£ãŸï¼Ÿæ®‹å¿µandroidã¦ã‚™ã—ãŸï½žã„ã¤ã‹ã‚‰Androidã‚’Javaã ã¨éŒ¯è¦šã—ã¦ã„ãŸï¼Ÿï½ž
kana321 2014/11/10
()

ã‚ã¨ã§èªã‚€

java

java8

slide

optional

null

programming

ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°

development
ãƒªãƒ³ã‚¯
ã€Œnullã€ã‚’ãƒ•ãƒ©ã‚°ã¨ã—ã¦ä½¿ã†ã®ã¯ã€ã‚„ã‚ãŸæ–¹ãŒã„ã„ - åœ°å¹³ç·šã«è¡Œã
null ã‚’ãƒ•ãƒ©ã‚°ã¨ã—ã¦ä½¿ã†ã®ã¯ã€ã‚„ã‚ãŸæ–¹ãŒã„ã„ã¨æ€ã„ã¾ã™ã€‚ null ã¯ã€ãŸã å¤‰æ•°ãŒåˆæœŸåŒ–ã•ã‚Œã¦ã„ãªã„ã“ã¨ã‚’è¡¨ã—ã¦ã„ã‚‹ã ã‘ã§ã™ã€‚ ã“ã®æ„å‘³ä»¥å¤–ã§ã€null ã‚’ä½¿ã‚ãªã„æ–¹ãŒã„ã„ã¨æ€ã„ã¾ã™ã€‚ null ã‚’ãƒ•ãƒ©ã‚°ã¨ã—ã¦ä½¿ã† ã€Œnull ã‚’ãƒ•ãƒ©ã‚°ã¨ã—ã¦ä½¿ã†ã€ã¨ã„ã†ã®ã¯ã€ã€Œnull ãªã‚‰ xxxxã€ã¨ã„ã†ã‚ˆã†ã«ã€null ãŒä½•ã‚‰ã‹ã®æ„å‘³ã‚’æŒã£ã¦ä½¿ã‚ã‚Œã¦ã„ã‚‹ã“ã¨ã‚’æŒ‡ã—ã¾ã™ã€‚ ä¾‹ãˆã°ã€ä¸‹è¨˜ã®ã‚³ãƒ¼ãƒ‰ã§ã¯ã€Œnull ã¯ã‚²ã‚¹ãƒˆãƒ¦ãƒ¼ã‚¶ã‚’æŒ‡ã™ãƒ•ãƒ©ã‚°ã€ã¨ã—ã¦ä½¿ã‚ã‚Œã¦ã„ã¾ã™ã€‚ /** * ãƒ¦ãƒ¼ã‚¶ç”¨ã®ãƒ˜ãƒƒãƒ€ã‚’ä½œã‚‹å‡¦ç† */ public String createHeader(User user){ (â€¦ä¸ç•¥â€¦) String name; if(user != null){ name = user.getName(); }else{ name = "Guest"; // null ãªã‚‰ã‚²ã‚¹ãƒˆãƒ¦ãƒ¼ã‚¶ } å•é¡Œç‚¹ ã“ã‚Œã®
kana321 2013/04/15
**

ã‚½ãƒ•ãƒˆã‚¦ã‚§ã‚¢é–‹ç™º

()

java

ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°

null

ãƒ—ãƒã‚°ãƒ©ãƒ

programming

ã“ã‚Œã¯ã²ã©ã„

Note
ãƒªãƒ³ã‚¯
ã€Œæ·¡è·¯å³¶ã®é›»è»Šã®é‹è¡ŒçŠ¶æ³ã‚’èžã„ãŸè©±ã€ã‚’ã‚·ã‚¹ãƒ†ãƒ é–‹ç™ºã«ç½®ãæ›ãˆã¦ã¿ã‚‹ - æ—¥ã€…å¸¸ã€…
æ°—è±¡åºã®åœ°éœ‡æƒ…å ±|å¹³æˆ25å¹´04æœˆ13æ—¥05æ™‚48åˆ† æ°—è±¡åºç™ºè¡¨ 4/13ã®AM5:33ã«M6.0ã‚‰ã—ã„åœ°éœ‡ãŒã‚ã‚Šã¾ã—ãŸã€‚å„åœ°ã§å¤§ããªè¢«å®³ãŒç„¡ã„ã“ã¨ã‚’ç¥ˆã‚Šã¤ã¤ã€‚ ãƒ•ã‚¸ãƒ†ãƒ¬ãƒ“ã®ã‚¢ãƒŠã‚¦ãƒ³ã‚µãƒ¼ã•ã‚“ãŒæ·¡è·¯å³¶ã®é›»è»Šã®çŠ¶æ³ã‚’èžã„ãŸã¨è¨€ã†è©± ã€æ”¾é€äº‹æ•…ã€‘ãƒ•ã‚¸ãƒ†ãƒ¬ãƒ“ãŒæ·¡è·¯å³¶æ°‘ã«ã€Œé›»è»Šå‹•ã„ã¦ã¾ã™ã‹?ã€ã¨è³ªå• ã€Œæ·¡è·¯å³¶ã¯é›»è»Šã‚ã‚Šã¾ã›ã‚“ã€ - NAVER ã¾ã¨ã‚ ã ã„ãŸã„è¦‹ã¦ã‚‹ã¨ã€Œé›»è»Šç„¡ã„ã®ã‚’çŸ¥ã‚‰ãšã«èžã„ã¦ã—ã¾ã£ãŸã€ã®ã‚’å©ãå‘ãã«æ€ãˆã¾ã™ã€‚å®Ÿéš›ã®ã¨ã“ã‚ã€èžã„ãŸã“ã¨è‡ªä½“ã¯NGãªã®ã§ã—ã‚‡ã†ãŒã€ã“ã‚Œã‚’ã‚·ã‚¹ãƒ†ãƒ é–‹ç™ºã®è©±ã«ç½®ãæ›ãˆã‚‹ã¨è¦‹ãˆã‚‹ã‚‚ã®ãŒã‚ã‚‹æ°—ãŒã—ã¾ã—ãŸã€‚ ä»¥é™ã¯Javaã®èªžå½™ã§æ›¸ãã¾ã™ãŒã€ã“ã‚Œã£ã¦ NullPointerException ã£ã½ã„ãªã¨ã€‚ ã‚³ãƒ¼ãƒ‰ã£ã½ã„ä½•ã‹ã§æ›¸ã„ã¦ã¿ã‚‹ ã“ã‚“ãªæ„Ÿã˜ã€‚ é‹è¡ŒçŠ¶æ³ = æ·¡è·¯å³¶.getè·¯ç·š().geté‹è¡ŒçŠ¶æ³(); getè·¯ç·š() ãŒä½•ã‚’è¿”ã™ã®ã‹çŸ¥ã‚‰ãªã„ã‘ã©ã€ã“ã‚ŒãŒ nu
kana321 2013/04/13
ä¾‹å¤–

()

programming

Java

é–‹ç™º

ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°

è€ƒãˆæ–¹

ãƒã‚¿

null

MyInterest
ãƒªãƒ³ã‚¯
Java ã®èªžå½™ã§ Maybe ã‚’èª¬æ˜Žã—ã¦ã¿ã‚‹ - ãã‚‹ãã‚‹ï½ž
java-jaã§ä¾‹å¤–å‡¦ç†ã®è©±ã‚’ã—ã¦ãã¾ã—ãŸ - è¥¿å°¾æ³°å’Œã®ã¯ã¦ãªãƒ€ã‚¤ã‚¢ãƒªãƒ¼ ã‚’èªã‚“ã§ã€‚ Maybe ã¯å€¤ãŒã‚ã‚‹ã‹ãªã„ã‹ã‚’åž‹ã§è¡¨ã™ã“ã¨ãŒã§ãã¾ã™ï¼ãã†ã€ç›´å’Œåž‹ãªã‚“ã§ã™ï¼ã¨ã‹è¨€ã‚ã‚Œã¦ã‚‚ã‚¤ãƒŸãƒ•ã ã¨æ€ã†ã®ã§ã™(ãƒªãƒ³ã‚¯å…ˆã®ã‚¨ãƒ³ãƒˆãƒªãŒãã†èª¬æ˜Žã—ã¦ã‚‹ã‚ã‘ã§ã¯ãªã„ã§ã™ãŒ)ã€‚ Java ã®èªžå½™ã§ Maybe ã®èª¬æ˜Žã‚’ã§ããŸã‚‰å¬‰ã—ã„äººã‚‚ã„ã‚‹ã‚“ã˜ã‚ƒãªã„ã‹ãªãã€ã¨ã‹ãªã‚“ã¨ã‹ã€‚ ãŸã ã—ã€æ›¸ã„ã¦ãŸã‚‰çµæ§‹é•·ããªã‚Šã¾ã—ãŸã€‚æ™‚é–“ãŒã‚ã‚‹äººã¯ã©ã†ãžã€‚ Maybeï¼Ÿ null ã‚ˆã‚Šå®‰å…¨ã«ã€Œå€¤ãŒãªã„ã“ã¨ã€ãŒæ‰±ãˆã‚‹ã‚‚ã®ã ã‚ˆ ã‚¹ã‚¿ãƒ¼ãƒˆåœ°ç‚¹ã¨ã—ã¦ã¯ã“ã‚Œã§ã„ã„ã§ã—ã‚‡ã†ã€‚ ä»¥é™ã§ã€ã€Œãªã‚“ã§å®‰å…¨ãªã®ï¼Ÿã€ã¨ã„ã†å…¨ã†ãªç–‘å•ã«ç”ãˆã¦ã¿ãŸã„ã¨æ€ã„ã¾ã™ã€‚ å•é¡Œç‚¹ int ã§èª¬æ˜Žã™ã‚‹ã¨ç…™ã«å·»ã„ã¦ã—ã¾ã†ã‚ˆã†ãªæ°—ãŒã—ãŸã®ã§ã€User ã‚¯ãƒ©ã‚¹ã‚’è¦‹ã¦ã¿ã¾ã™ã€‚ import java.util.*; class User { final String name;
kana321 2012/06/29
*ã‚ã¨ã§èªã‚€

null

java8

java

*Java

Maybe

ãƒ—ãƒã‚°ãƒ©ãƒŸãƒ³ã‚°

programming

ä¾‹å¤–å‡¦ç†

ã‚ã¨ã§èªã‚€
ãƒªãƒ³ã‚¯
1