addEntry(hash, key, value, index); returnnull; } 通过Hashtable的put底层源码,我们可以看到,方法体内,首先就对value值进行的判空操作,如果为空则抛出空指针异常;其次在计算hash值的时候,直接调用key的hashCode()方法,若keynull,自然也会报空指针异常,因此,我们在调用put方法存储键值对时,key与value都非null。
然后就一直没有明白 明明都赋值了 为什么还会这样 ,然后我把unique字段和非空字段去掉即//@Column(name = "zh", unique = true, nullable = false)就好了。
在hashtable中,对value进行了非空校验,而key,如果为空则会出现NullPointerException。 代码语言:javascript 代码运行次数:0 运行 if(value==null){thrownewNullPointerException();}// Makes sure the key is not already in the hashtable.Entry<?,?>tab[]=table;int hash=key.hashCode(); key如果为空,则h...
publicsynchronizedVput(Kkey,Vvalue){// 确认值不为空if(value==null){thrownewNullPointerException();// 如果值为null,则抛出空指针异常}// 确认值之前不存在Hashtable里Entry<?,?>tab[]=table;int hash=key.hashCode();// 如果key如果为null,调用这个方法会抛出空指针异常int index=(hash&0x7FFFFFFF)...
1062 - Duplicate entry 'aaa@' for key 'uk-email', Time: 0.005000s 1. 2. 3. 4. 5. 6. 此时对于唯一性来说是没问题的,可以保证业务的email的唯一性。假设随着业务的发展,此时需要增加手机号注册功能,那么表中就需要增加手机号字段,且需要保证手机号和邮箱的关联唯一性。
偶尔会出现报错null id in entry (don't flush the Session after an exception occurs),下面的2019-01-22 17:02:16,088 DEBUG Ylsdai.Service.BaseService -<log4net.Error>Exception during StringFormat: 输入字符串的格式不正确。 <format>Save.Exception=>null id in Ylsdai.Domain.Entity.AgentShopSale ...
System.out.println(key+":"+value); } 1. 2. 3. 4. 5. 6. 7. 取出map集合中所有元素的方式二:entrySet()方法。 AI检测代码解析 Set entrySet = map.entrySet(); Iterator it = entrySet.iterator(); while(it.hasNext()) { Map.Entry me = (Map.Entry)it.next(); ...
editEntry.putExtra(KEY_EXTRA_DATA_ID, listViewItempt1); startActivity(editEntry); } } }); } // For the go back button. public void viewdiarytoinitialdiary_backbutt(View v){ // Create and start new intent going back ot main page. ...
CacheKey(DefaultTaskArtifactStateRepository.java:126) 16:59:16 at org.gradle.api.internal.tasks.execution.ResolveBuildCacheKeyExecuter.doResolve(ResolveBuildCacheKeyExecuter.java:99) 16:59:16 at org.gradle.api.internal.tasks.execution.ResolveBuildCacheKeyExecuter.access$000(ResolveBuildCacheKeyExecuter....
mapping in the domaindir/config/login.conf file. I restarted the server, and installed a web app using the custom realm to restrict the access to a servlet, with BASIC auth mode. When entering my login & password in the login window i get the the ...