差異處
這裏顯示兩個版本的差異處。
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java:basic:string [2019/09/17 09:36] tony |
java:basic:string [2023/06/25 09:48] |
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| 行 1: | 行 1: | ||
| - | {{tag>java}} | ||
| - | ====== String ====== | ||
| - | ===== 有效率的寫法 ===== | ||
| - | ==== 宣告 ==== | ||
| - | 在fix findubg系列文章中有提到的寫法:([[java:code_quality:findbug:dm_string_void_ctor|DM_STRING_VOID_CTOR]]、[[java:code_quality:findbug:dm_string_ctor|DM_STRING_CTOR]]) | ||
| - | <code java> | ||
| - | String bad1 = new String("test"); | ||
| - | String bad2 = new String(); | ||
| - | </code> | ||
| - | V.S. | ||
| - | <code java> | ||
| - | String good1 = "test"; | ||
| - | String good2 = ""; | ||
| - | </code> | ||
| - | 主要原理是由於"test"與""在編譯時就就已決定放置於Constant Pool。new String("test")在編譯時也會將"test"放到Constant Pool，然後Runtime會再去做new String的動作。這是不必要的浪費! | ||
| - | ===== Reference ===== | ||
| - | * [[http://hi.baidu.com/boywell/item/d5ee5b0cc0af55c875cd3cfd|Java对String字符串对象的创建,管理和“+”运算符的实现]] | ||
| - | * [[https://javapapers.com/java/java-string-vs-stringbuilder-vs-stringbuffer-concatenation-performance-micro-benchmark/|Java String vs StringBuilder vs StringBuffer Concatenation Performance Micro Benchmark]] | ||
| - | |||
| - | ===== ===== | ||
| - | ---- | ||
| - | \\ | ||
| - | ~~DISQUS~~ | ||
