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Java string null check by != null or !str.equals(null)? [duplicate]

由 久未见 提交于 2021-02-07 18:20:50
问题 This question already has answers here : Java null check why use == instead of .equals() (16 answers) Closed 7 years ago . What's the best way to check for not null values in java. String query ="abcd"; query != null vs !query.equals(null). which is better?why? 回答1: 1st one is better (and the only option ), because 2nd one will throw NPE , when your value is actually null . As simple as that. Try this out: String str = null; str.equals(null); // will throw `NPE`. So basically, the test which

Future.get() gets interrupted always with an InterruptedException

由 99封情书 提交于 2021-02-07 13:48:30
问题 I have a WEIRD problem with Future.get() in Java. It returns always with an InterruptedException, however the weird thing is that the cause of the Exception is null, so I cant tell who interrupted me.. It gets even worse because I check before calling get(), and the job Future has to do is already done. Here is the code responsible for the output below. f is the Future , and the callable returns a HashMap where Agent is not really relevant. Sorry if there are too many printlines, I'm just

Future.get() gets interrupted always with an InterruptedException

由 你说的曾经没有我的故事 提交于 2021-02-07 13:47:58
问题 I have a WEIRD problem with Future.get() in Java. It returns always with an InterruptedException, however the weird thing is that the cause of the Exception is null, so I cant tell who interrupted me.. It gets even worse because I check before calling get(), and the job Future has to do is already done. Here is the code responsible for the output below. f is the Future , and the callable returns a HashMap where Agent is not really relevant. Sorry if there are too many printlines, I'm just

C - Setting a struct to null (incompatible types in assignment)

由 我只是一个虾纸丫 提交于 2021-02-06 12:50:05
问题 I have the following struct: struct elem { int number; char character; }; struct item { struct elem element; }; and the following function: void init(struct item *wrapper) { assert(wrapper != NULL); wrapper->element = NULL; } item->element = NULL yields a incompatible types in assignment . Why is that? Shouldn't setting a struct to NULL be okay? 回答1: In C NULL is generally defined as the following #define NULL ((void*)0) This means that it's a pointer value. In this case your attempting to

C - Setting a struct to null (incompatible types in assignment)

由 耗尽温柔 提交于 2021-02-06 12:47:32
问题 I have the following struct: struct elem { int number; char character; }; struct item { struct elem element; }; and the following function: void init(struct item *wrapper) { assert(wrapper != NULL); wrapper->element = NULL; } item->element = NULL yields a incompatible types in assignment . Why is that? Shouldn't setting a struct to NULL be okay? 回答1: In C NULL is generally defined as the following #define NULL ((void*)0) This means that it's a pointer value. In this case your attempting to

WHERE clause great than zero still showing zero when using CASE functions

由 泪湿孤枕 提交于 2021-02-05 11:19:26
问题 I am trying the WHERE clause to filter out other data I dont want. SELECT `post_id`, MAX(CASE WHEN `meta_key` = 'vlaue_1' THEN `meta_value` ELSE NULL END) as 'Customer', MAX(CASE WHEN `meta_key` = 'value_2' THEN `meta_value` ELSE NULL END) as 'DeliveryDate', MAX(CASE WHEN `meta_key` = 'value_3' THEN `meta_value` ELSE NULL END) as 'DeliveryTime', MAX(CASE WHEN `meta_key` = 'vlaue_4' THEN `meta_value` ELSE NULL END) as 'DeliveryType' FROM wp_postmeta WHERE 'Customer' > 0 GROUP BY `post_id`

Source code string cannot contain null bytes [closed]

由 天涯浪子 提交于 2021-02-05 10:44:05
问题 Closed. This question needs debugging details. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 3 years ago . Improve this question So i had 676 line program, Now i have had a issue in the past when I opened the file all my code had disapeared so this time i made a backup. However when I try to copy and paste my backedup code then run it, it gives me this syntax error: Source code string cannot contain null

How to handle nulls in an Elasticsearch index

由 微笑、不失礼 提交于 2021-02-05 07:17:15
问题 I have a SQL table that I am exporting to Elasticsearch. One of the columns is a numeric field that is nullable, with nulls in some of the records. When we try to index the table, we get this error: One of the ETL (BigQuery -> ElasticSearch) jobs for Table : MLS has been ES Failed Chunk of 10000 from index 20000 possibly due to incompatible objects. Failing BigQuery Table: MLS Stack Trace of the error: Traceback (most recent call last): File "/Users/asif/zodiacbackend/zodiacbackend/tasks.py",

How to handle nulls in an Elasticsearch index

由 做~自己de王妃 提交于 2021-02-05 07:16:25
问题 I have a SQL table that I am exporting to Elasticsearch. One of the columns is a numeric field that is nullable, with nulls in some of the records. When we try to index the table, we get this error: One of the ETL (BigQuery -> ElasticSearch) jobs for Table : MLS has been ES Failed Chunk of 10000 from index 20000 possibly due to incompatible objects. Failing BigQuery Table: MLS Stack Trace of the error: Traceback (most recent call last): File "/Users/asif/zodiacbackend/zodiacbackend/tasks.py",

linux线程基本编程

由 你离开我真会死。 提交于 2021-02-01 04:02:30
索引： 1.创建线程pthread_create 2.等待线程结束pthread_join 3.分离线程pthread_detach 4.创建线程键pthread_key_create 5.删除线程键pthread_key_delete 6.设置线程数据pthread_setspecific 7.获取线程数据pthread_getspecific 8.获取线程标示符pthread_self 9.比较线程pthread_equal 10.一次执行pthread_once 11.出让执行权sched_yield 12.修改优先级pthread_setschedparam 13.获取优先级pthread_getschedparam 14.发送信号pthread_kill 15.设置线程掩码pthread_sigmask 16.终止线程pthread_exit 17.退出线程pthread_cancel 18.允许/禁止退出线程pthread_setcancelstate 19.设置退出类型pthread_setcanceltype 20.创建退出点pthread_testcancel 21.压入善后处理函数 22.弹出善后处理函数 -------------------------------------------------------------------------------
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